feat: I am going to throw my computer out a window

39 files changed, 1411 insertions, 302 deletions

diff --git a/assets/shaders/basic.glsl b/assets/shaders/basic.glsl
deleted file mode 100644
index f6016f7..0000000
--- a/assets/shaders/basic.glsl
+++ /dev/null
@@ -1,31 +0,0 @@
-#type vertex
-#version 330 core
-
-layout(location = 0) in vec3 a_Position;
-layout(location = 1) in vec4 a_Color;
-
-uniform mat4 u_ViewProjection;
-uniform mat4 u_Transform;
-
-out vec3 v_Position;
-out vec4 v_Color;
-
-void main()
-{
-    v_Position = a_Position;
-    v_Color = a_Color;
-    gl_Position = u_ViewProjection * u_Transform * vec4(a_Position, 1.0);
-}
-
-#type fragment
-#version 330 core
-
-layout(location = 0) out vec4 color;
-
-in vec3 v_Position;
-in vec4 v_Color;
-
-void main()
-{
-    color = v_Color;
-}
diff --git a/assets/shaders/compute.glsl b/assets/shaders/compute.glsl
deleted file mode 100644
index 9a36a84..0000000
--- a/assets/shaders/compute.glsl
+++ /dev/null
@@ -1,24 +0,0 @@
-#type compute
-#version 430 core
-
-layout(local_size_x = 256) in;
-
-layout(std430, binding = 0) buffer InputBuffer
-{
-    float data[];
-} inputBuffer;
-
-layout(std430, binding = 1) buffer OutputBuffer
-{
-    float data[];
-} outputBuffer;
-
-uniform float u_Scale;
-uniform float u_Offset;
-
-void main()
-{
-    uint index = gl_GlobalInvocationID.x;
-    float inputValue = inputBuffer.data[index];
-    outputBuffer.data[index] = inputValue * u_Scale + u_Offset;
-}
diff --git a/assets/shaders/geodesic.glsl b/assets/shaders/geodesic.glsl
new file mode 100644
index 0000000..6b077be
--- /dev/null
+++ b/assets/shaders/geodesic.glsl
@@ -0,0 +1,215 @@
+#version 430
+layout(local_size_x = 16, local_size_y = 16) in;
+
+layout(binding = 0, rgba8) writeonly uniform image2D outImage;
+
+layout(std140, binding = 1) uniform Camera 
+{
+    vec3 camPos;     float _pad0;
+    vec3 camRight;   float _pad1;
+    vec3 camUp;      float _pad2;
+    vec3 camForward; float _pad3;
+    float tanHalfFov;
+    float aspect;
+    bool moving;
+    int   _pad4;
+} cam;
+
+layout(std140, binding = 2) uniform Disk 
+{
+    float disk_r1;
+    float disk_r2;
+    float disk_num;
+    float thickness;
+};
+
+layout(std140, binding = 3) uniform Objects 
+{
+    int numObjects;
+    vec4 objPosRadius[16];
+    vec4 objColor[16];
+    float mass[16]; 
+};
+
+const float SagA_rs = 1.269e10;
+const float D_LAMBDA = 1e7;
+const double ESCAPE_R = 1e30;
+
+vec4 objectColor = vec4(0.0);
+vec3 hitCenter = vec3(0.0);
+float hitRadius = 0.0;
+
+struct Ray 
+{
+    float x, y, z, radius, theta, phi;
+    float dRadius, dTheta, dPhi;
+    float energy, angularMomentum;
+};
+
+Ray InitRay(vec3 position, vec3 direction) 
+{
+    Ray ray;
+    ray.x = position.x; 
+    ray.y = position.y; 
+    ray.z = position.z;
+    ray.radius = length(position);
+    ray.theta = acos(position.z / ray.radius);
+    ray.phi = atan(position.y, position.x);
+
+    float dx = direction.x, dy = direction.y, dz = direction.z;
+    ray.dRadius = sin(ray.theta) * cos(ray.phi) * dx + sin(ray.theta) * sin(ray.phi) * dy + cos(ray.theta) * dz;
+    ray.dTheta = (cos(ray.theta) * cos(ray.phi) * dx + cos(ray.theta) * sin(ray.phi) * dy - sin(ray.theta) * dz) / ray.radius;
+    ray.dPhi = (-sin(ray.phi) * dx + cos(ray.phi) * dy) / (ray.radius * sin(ray.theta));
+
+    ray.angularMomentum = ray.radius * ray.radius * sin(ray.theta) * ray.dPhi;
+    float f = 1.0 - SagA_rs / ray.radius;
+    float dt_dL = sqrt((ray.dRadius * ray.dRadius) / f + ray.radius * ray.radius * (ray.dTheta * ray.dTheta + sin(ray.theta) * sin(ray.theta) * ray.dPhi * ray.dPhi));
+    ray.energy = f * dt_dL;
+
+    return ray;
+}
+
+bool Intercept(Ray ray, float schwarzschildRadius) 
+{
+    return ray.radius <= schwarzschildRadius;
+}
+
+bool InterceptObject(Ray ray) 
+{
+    vec3 position = vec3(ray.x, ray.y, ray.z);
+    
+    for (int i = 0; i < numObjects; ++i) 
+    {
+        vec3 center = objPosRadius[i].xyz;
+        float radius = objPosRadius[i].w;
+        
+        if (distance(position, center) <= radius) 
+        {
+            objectColor = objColor[i];
+            hitCenter = center;
+            hitRadius = radius;
+            return true;
+        }
+    }
+    
+    return false;
+}
+
+void GeodesicRHS(Ray ray, out vec3 derivatives1, out vec3 derivatives2) 
+{
+    float radius = ray.radius, theta = ray.theta;
+    float dRadius = ray.dRadius, dTheta = ray.dTheta, dPhi = ray.dPhi;
+    float f = 1.0 - SagA_rs / radius;
+    float dt_dL = ray.energy / f;
+
+    derivatives1 = vec3(dRadius, dTheta, dPhi);
+    derivatives2.x = -(SagA_rs / (2.0 * radius * radius)) * f * dt_dL * dt_dL
+         + (SagA_rs / (2.0 * radius * radius * f)) * dRadius * dRadius
+         + radius * (dTheta * dTheta + sin(theta) * sin(theta) * dPhi * dPhi);
+    derivatives2.y = -2.0 * dRadius * dTheta / radius + sin(theta) * cos(theta) * dPhi * dPhi;
+    derivatives2.z = -2.0 * dRadius * dPhi / radius - 2.0 * cos(theta) / sin(theta) * dTheta * dPhi;
+}
+
+void RK4Step(inout Ray ray, float deltaLambda) 
+{
+    vec3 k1a, k1b;
+    GeodesicRHS(ray, k1a, k1b);
+
+    ray.radius += deltaLambda * k1a.x;
+    ray.theta += deltaLambda * k1a.y;
+    ray.phi += deltaLambda * k1a.z;
+    ray.dRadius += deltaLambda * k1b.x;
+    ray.dTheta += deltaLambda * k1b.y;
+    ray.dPhi += deltaLambda * k1b.z;
+
+    ray.x = ray.radius * sin(ray.theta) * cos(ray.phi);
+    ray.y = ray.radius * sin(ray.theta) * sin(ray.phi);
+    ray.z = ray.radius * cos(ray.theta);
+}
+
+bool CrossesEquatorialPlane(vec3 oldPosition, vec3 newPosition) 
+{
+    bool crossed = (oldPosition.y * newPosition.y < 0.0);
+    float radius = length(vec2(newPosition.x, newPosition.z));
+    return crossed && (radius >= disk_r1 && radius <= disk_r2);
+}
+
+void main() 
+{
+    ivec2 pixel = ivec2(gl_GlobalInvocationID.xy);
+    int width = imageSize(outImage).x;
+    int height = imageSize(outImage).y;
+    
+    if (pixel.x >= width || pixel.y >= height) 
+        return;
+
+    float u = (2.0 * (pixel.x + 0.5) / width - 1.0) * cam.aspect * cam.tanHalfFov;
+    float v = (1.0 - 2.0 * (pixel.y + 0.5) / height) * cam.tanHalfFov;
+    vec3 direction = normalize(u * cam.camRight - v * cam.camUp + cam.camForward);
+    Ray ray = InitRay(cam.camPos, direction);
+
+    vec4 color = vec4(0.0);
+    vec3 prevPosition = vec3(ray.x, ray.y, ray.z);
+    float lambda = 0.0;
+
+    bool hitBlackHole = false;
+    bool hitDisk = false;
+    bool hitObject = false;
+
+    int steps = cam.moving ? 60000 : 60000;
+
+    for (int i = 0; i < steps; ++i) 
+    {
+        if (Intercept(ray, SagA_rs)) 
+        { 
+            hitBlackHole = true; 
+            break; 
+        }
+        
+        RK4Step(ray, D_LAMBDA);
+        lambda += D_LAMBDA;
+
+        vec3 newPosition = vec3(ray.x, ray.y, ray.z);
+        
+        if (CrossesEquatorialPlane(prevPosition, newPosition)) 
+        { 
+            hitDisk = true; 
+            break; 
+        }
+        
+        if (InterceptObject(ray)) 
+        { 
+            hitObject = true; 
+            break; 
+        }
+        
+        prevPosition = newPosition;
+        
+        if (ray.radius > ESCAPE_R) 
+            break;
+    }
+
+    if (hitDisk) 
+    {
+        double radius = length(vec3(ray.x, ray.y, ray.z)) / disk_r2;
+        vec3 diskColor = vec3(1.0, radius, 0.2);
+        color = vec4(diskColor, radius);
+    } 
+    else if (hitBlackHole) 
+        color = vec4(0.0, 0.0, 0.0, 1.0);
+    else if (hitObject) 
+    {
+        vec3 position = vec3(ray.x, ray.y, ray.z);
+        vec3 normal = normalize(position - hitCenter);
+        vec3 viewDirection = normalize(cam.camPos - position);
+        float ambient = 0.1;
+        float diffuse = max(dot(normal, viewDirection), 0.0);
+        float intensity = ambient + (1.0 - ambient) * diffuse;
+        vec3 shaded = objectColor.rgb * intensity;
+        color = vec4(shaded, objectColor.a);
+    } 
+    else 
+        color = vec4(0.0);
+
+    imageStore(outImage, pixel, color);
+}
diff --git a/assets/shaders/grid.glsl b/assets/shaders/grid.glsl
new file mode 100644
index 0000000..66096c4
--- /dev/null
+++ b/assets/shaders/grid.glsl
@@ -0,0 +1,19 @@
+#type vertex
+#version 330 core
+layout (location = 0) in vec3 aPos;
+
+uniform mat4 viewProj;
+
+void main()
+{
+    gl_Position = viewProj * vec4(aPos, 1.0);
+}
+
+#type fragment
+#version 330 core
+out vec4 FragColor;
+
+void main()
+{
+    FragColor = vec4(0.5, 0.5, 0.5, 0.3);
+}
diff --git a/assets/shaders/image_processing.glsl b/assets/shaders/image_processing.glsl
deleted file mode 100644
index 3a05425..0000000
--- a/assets/shaders/image_processing.glsl
+++ /dev/null
@@ -1,31 +0,0 @@
-#type compute
-#version 430 core
-
-layout(local_size_x = 16, local_size_y = 16) in;
-
-layout(binding = 0) uniform sampler2D u_InputTexture;
-layout(binding = 1, rgba8) uniform image2D u_OutputTexture;
-
-uniform vec2 u_TextureSize;
-uniform float u_Brightness;
-uniform float u_Contrast;
-uniform float u_Saturation;
-
-void main()
-{
-    ivec2 pixelCoord = ivec2(gl_GlobalInvocationID.xy);
-    
-    if (pixelCoord.x >= int(u_TextureSize.x) || pixelCoord.y >= int(u_TextureSize.y))
-        return;
-    
-    vec2 texCoord = (vec2(pixelCoord) + 0.5) / u_TextureSize;
-    vec4 color = texture(u_InputTexture, texCoord);
-    
-    color.rgb = (color.rgb - 0.5) * u_Contrast + 0.5 + u_Brightness;
-    
-    float luminance = dot(color.rgb, vec3(0.299, 0.587, 0.114));
-    color.rgb = mix(vec3(luminance), color.rgb, u_Saturation);
-    color.rgb = clamp(color.rgb, 0.0, 1.0);
-    
-    imageStore(u_OutputTexture, pixelCoord, color);
-}
diff --git a/assets/shaders/particle_system.glsl b/assets/shaders/particle_system.glsl
deleted file mode 100644
index 1e9d435..0000000
--- a/assets/shaders/particle_system.glsl
+++ /dev/null
@@ -1,58 +0,0 @@
-#type compute
-#version 430 core
-
-layout(local_size_x = 256) in;
-
-struct Particle
-{
-    vec4 position;
-    vec4 velocity;
-    vec4 color;
-};
-
-layout(std430, binding = 0) buffer ParticleBuffer
-{
-    Particle particles[];
-} particleBuffer;
-
-uniform float u_DeltaTime;
-uniform vec3 u_Gravity;
-uniform vec3 u_EmitterPosition;
-uniform float u_EmissionRate;
-uniform float u_ParticleLifetime;
-uniform float u_Time;
-
-void main()
-{
-    uint index = gl_GlobalInvocationID.x;
-    
-    if (index >= particles.length())
-        return;
-    
-    Particle particle = particleBuffer.particles[index];
-    
-    particle.position.w -= u_DeltaTime;
-    
-    if (particle.position.w <= 0.0)
-    {
-        particle.position.xyz = u_EmitterPosition;
-        particle.position.w = u_ParticleLifetime;
-        
-        float angle = fract(sin(dot(vec2(index, u_Time), vec2(12.9898, 78.233))) * 43758.5453) * 2.0 * 3.14159;
-        float speed = 2.0 + fract(sin(dot(vec2(index + 1, u_Time), vec2(12.9898, 78.233))) * 43758.5453) * 3.0;
-        particle.velocity.xyz = vec3(cos(angle) * speed, 5.0, sin(angle) * speed);
-        particle.velocity.w = 1.0;
-        
-        particle.color = vec4(1.0, 0.5 + 0.5 * fract(sin(index * 123.456) * 43758.5453), 0.2, 1.0);
-    }
-    else
-    {
-        particle.velocity.xyz += u_Gravity * u_DeltaTime;
-        particle.position.xyz += particle.velocity.xyz * u_DeltaTime;
-        
-        float lifeRatio = particle.position.w / u_ParticleLifetime;
-        particle.color.a = lifeRatio;
-    }
-    
-    particleBuffer.particles[index] = particle;
-}
diff --git a/assets/shaders/quad.glsl b/assets/shaders/quad.glsl
new file mode 100644
index 0000000..57693a6
--- /dev/null
+++ b/assets/shaders/quad.glsl
@@ -0,0 +1,25 @@
+#type vertex
+#version 330 core
+layout(location = 0) in vec2 a_Pos;
+layout(location = 1) in vec2 a_TexCoord;
+
+out vec2 v_TexCoord;
+
+void main()
+{
+    gl_Position = vec4(a_Pos.xy, 0.0, 1.0);
+    v_TexCoord = a_TexCoord;
+}
+
+#type fragment
+#version 330 core
+out vec4 FragColor;
+
+in vec2 v_TexCoord;
+
+uniform sampler2D screenTexture;
+
+void main()
+{
+    FragColor = texture(screenTexture, v_TexCoord);
+}
diff --git a/assets/shaders/texture_processor.glsl b/assets/shaders/texture_processor.glsl
deleted file mode 100644
index a234ac8..0000000
--- a/assets/shaders/texture_processor.glsl
+++ /dev/null
@@ -1,43 +0,0 @@
-#type compute
-#version 430 core
-
-layout(local_size_x = 16, local_size_y = 16) in;
-
-layout(binding = 0) uniform sampler2D u_InputTexture;
-layout(binding = 1, rgba8) uniform image2D u_OutputTexture;
-
-uniform vec2 u_TextureSize;
-uniform float u_Time;
-uniform float u_Brightness;
-uniform float u_Contrast;
-uniform float u_Saturation;
-
-void main()
-{
-    ivec2 pixelCoord = ivec2(gl_GlobalInvocationID.xy);
-    
-    if (pixelCoord.x >= int(u_TextureSize.x) || pixelCoord.y >= int(u_TextureSize.y))
-        return;
-    
-    vec2 texCoord = (vec2(pixelCoord) + 0.5) / u_TextureSize;
-    vec4 color = texture(u_InputTexture, texCoord);
-    
-    float time = u_Time * 2.0f;
-    float u = texCoord.x;
-    float v = texCoord.y;
-    
-    float wave = sin(u * 10.0f + time) * cos(v * 10.0f + time * 0.5f);
-    wave = (wave + 1.0f) * 0.5f;
-    
-    vec4 animatedColor = vec4(wave, 1.0f - wave, (u + v) * 0.5f, 1.0f);
-    color = mix(color, animatedColor, 0.3f);
-    
-    color.rgb = (color.rgb - 0.5) * u_Contrast + 0.5 + u_Brightness;
-    
-    float luminance = dot(color.rgb, vec3(0.299, 0.587, 0.114));
-    color.rgb = mix(vec3(luminance), color.rgb, u_Saturation);
-    
-    color.rgb = clamp(color.rgb, 0.0, 1.0);
-    
-    imageStore(u_OutputTexture, pixelCoord, color);
-}
diff --git a/assets/shaders/textured.glsl b/assets/shaders/textured.glsl
deleted file mode 100644
index ad135fe..0000000
--- a/assets/shaders/textured.glsl
+++ /dev/null
@@ -1,41 +0,0 @@
-#type vertex
-#version 330 core
-
-layout(location = 0) in vec3 a_Position;
-layout(location = 1) in vec4 a_Color;
-layout(location = 2) in vec2 a_TexCoord;
-
-uniform mat4 u_ViewProjection;
-uniform mat4 u_Transform;
-
-out vec3 v_Position;
-out vec4 v_Color;
-out vec2 v_TexCoord;
-
-void main()
-{
-    v_Position = a_Position;
-    v_Color = a_Color;
-    v_TexCoord = a_TexCoord;
-    gl_Position = u_ViewProjection * u_Transform * vec4(a_Position, 1.0);
-}
-
-#type fragment
-#version 330 core
-
-layout(location = 0) out vec4 color;
-
-in vec3 v_Position;
-in vec4 v_Color;
-in vec2 v_TexCoord;
-
-uniform sampler2D u_Texture;
-
-void main()
-{
-    vec4 texColor = texture(u_Texture, v_TexCoord);
-    if (texColor.rgb == vec3(0.0))
-        color = v_Color;
-    else
-        color = v_Color * texColor;
-}
diff --git a/src/core/camera.cpp b/src/core/camera.cpp
index f580191..43cb1ee 100644
--- a/src/core/camera.cpp
+++ b/src/core/camera.cpp
@@ -28,22 +28,32 @@ namespace Donut
 
     void Camera::recalculate_view_matrix()
     {
-        float pitch = glm::radians(m_rotation.x);
-        float yaw   = glm::radians(m_rotation.y);
-        float roll  = glm::radians(m_rotation.z);
+        if (m_camera_mode == CameraMode::FPS)
+        {
+            float pitch = glm::radians(m_rotation.x);
+            float yaw   = glm::radians(m_rotation.y);
+            float roll  = glm::radians(m_rotation.z);
 
-        glm::vec3 direction;
-        direction.x = cos(yaw) * cos(pitch);
-        direction.y = sin(pitch);
-        direction.z = sin(yaw) * cos(pitch);
+            glm::vec3 direction;
+            direction.x = cos(yaw) * cos(pitch);
+            direction.y = sin(pitch);
+            direction.z = sin(yaw) * cos(pitch);
 
-        glm::vec3 world_up(0.0f, 1.0f, 0.0f);
-        glm::vec3 front = glm::normalize(direction);
-        glm::vec3 right = glm::normalize(glm::cross(front, world_up));
-        glm::vec3 up    = glm::normalize(glm::cross(right, front));
+            glm::vec3 world_up(0.0f, 1.0f, 0.0f);
+            glm::vec3 front = glm::normalize(direction);
+            glm::vec3 right = glm::normalize(glm::cross(front, world_up));
+            glm::vec3 up    = glm::normalize(glm::cross(right, front));
 
-        m_view_matrix           = glm::lookAt(m_position, m_position + front, up);
-        m_view_projection_matrix = m_projection_matrix * m_view_matrix;
+            m_view_matrix           = glm::lookAt(m_position, m_position + front, up);
+            m_view_projection_matrix = m_projection_matrix * m_view_matrix;
+        }
+        else if (m_camera_mode == CameraMode::Orbital)
+        {
+            glm::vec3 position = get_orbital_position();
+            glm::vec3 world_up(0.0f, 1.0f, 0.0f);
+            m_view_matrix = glm::lookAt(position, m_target, world_up);
+            m_view_projection_matrix = m_projection_matrix * m_view_matrix;
+        }
     }
 
     glm::vec3 Camera::get_forward_direction() const
@@ -72,58 +82,152 @@ namespace Donut
 
     void Camera::on_mouse_move(float x_offset, float y_offset, bool constrain_pitch)
     {
-        x_offset *= m_mouse_sensitivity;
-        y_offset *= m_mouse_sensitivity;
+        if (m_camera_mode == CameraMode::FPS)
+        {
+            x_offset *= m_mouse_sensitivity;
+            y_offset *= m_mouse_sensitivity;
 
-        m_rotation.y += x_offset;
-        m_rotation.x += y_offset;
+            m_rotation.y += x_offset;
+            m_rotation.x += y_offset;
 
-        if (constrain_pitch)
-        {
-            if (m_rotation.x > 89.0f)
-                m_rotation.x = 89.0f;
-            if (m_rotation.x < -89.0f)
-                m_rotation.x = -89.0f;
-        }
+            if (constrain_pitch)
+            {
+                if (m_rotation.x > 89.0f)
+                    m_rotation.x = 89.0f;
+                if (m_rotation.x < -89.0f)
+                    m_rotation.x = -89.0f;
+            }
 
-        recalculate_view_matrix();
+            recalculate_view_matrix();
+        }
     }
 
     void Camera::move_forward(float delta_time)
     {
-        m_position += get_forward_direction() * m_movement_speed * delta_time;
-        recalculate_view_matrix();
+        if (m_camera_mode == CameraMode::FPS)
+        {
+            m_position += get_forward_direction() * m_movement_speed * delta_time;
+            recalculate_view_matrix();
+        }
     }
 
     void Camera::move_backward(float delta_time)
     {
-        m_position -= get_forward_direction() * m_movement_speed * delta_time;
-        recalculate_view_matrix();
+        if (m_camera_mode == CameraMode::FPS)
+        {
+            m_position -= get_forward_direction() * m_movement_speed * delta_time;
+            recalculate_view_matrix();
+        }
     }
 
     void Camera::move_right(float delta_time)
     {
-        m_position += get_right_direction() * m_movement_speed * delta_time;
-        recalculate_view_matrix();
+        if (m_camera_mode == CameraMode::FPS)
+        {
+            m_position += get_right_direction() * m_movement_speed * delta_time;
+            recalculate_view_matrix();
+        }
     }
 
     void Camera::move_left(float delta_time)
     {
-        m_position -= get_right_direction() * m_movement_speed * delta_time;
-        recalculate_view_matrix();
+        if (m_camera_mode == CameraMode::FPS)
+        {
+            m_position -= get_right_direction() * m_movement_speed * delta_time;
+            recalculate_view_matrix();
+        }
     }
 
     void Camera::move_up(float delta_time)
     {
-        glm::vec3 world_up(0.0f, 1.0f, 0.0f);
-        m_position += world_up * m_movement_speed * delta_time;
-        recalculate_view_matrix();
+        if (m_camera_mode == CameraMode::FPS)
+        {
+            glm::vec3 world_up(0.0f, 1.0f, 0.0f);
+            m_position += world_up * m_movement_speed * delta_time;
+            recalculate_view_matrix();
+        }
     }
 
     void Camera::move_down(float delta_time)
     {
-        glm::vec3 world_up(0.0f, 1.0f, 0.0f);
-        m_position -= world_up * m_movement_speed * delta_time;
+        if (m_camera_mode == CameraMode::FPS)
+        {
+            glm::vec3 world_up(0.0f, 1.0f, 0.0f);
+            m_position -= world_up * m_movement_speed * delta_time;
+            recalculate_view_matrix();
+        }
+    }
+
+    void Camera::set_orbital_mode(bool enabled)
+    {
+        m_camera_mode = enabled ? CameraMode::Orbital : CameraMode::FPS;
+        recalculate_view_matrix();
+    }
+
+    glm::vec3 Camera::get_orbital_position() const
+    {
+        float clamped_elevation = glm::clamp(m_elevation, 0.01f, float(M_PI) - 0.01f);
+        return glm::vec3(
+            m_radius * sin(clamped_elevation) * cos(m_azimuth),
+            m_radius * cos(clamped_elevation),
+            m_radius * sin(clamped_elevation) * sin(m_azimuth)
+        );
+    }
+
+    void Camera::process_orbital_mouse_move(double x, double y)
+    {
+        if (m_dragging && !m_panning) 
+        {
+            float dx = float(x - m_orbital_last_x);
+            float dy = float(y - m_orbital_last_y);
+            
+            m_azimuth += dx * m_orbit_speed;
+            m_elevation -= dy * m_orbit_speed;
+            m_elevation = glm::clamp(m_elevation, 0.01f, float(M_PI) - 0.01f);
+        }
+        
+        m_orbital_last_x = x;
+        m_orbital_last_y = y;
+        update_orbital_state();
         recalculate_view_matrix();
     }
+
+    void Camera::process_orbital_mouse_button(int button, int action, int mods)
+    {
+        if (button == GLFW_MOUSE_BUTTON_LEFT) 
+        {
+            if (action == GLFW_PRESS) 
+            {
+                m_dragging = true;
+                m_panning = false;
+            } 
+            else if (action == GLFW_RELEASE) 
+            {
+                m_dragging = false;
+                m_panning = false;
+            }
+        }
+        update_orbital_state();
+    }
+
+    void Camera::process_orbital_scroll(double x_offset, double y_offset)
+    {
+        m_radius -= y_offset * m_zoom_speed;
+        m_radius = glm::clamp(m_radius, m_min_radius, m_max_radius);
+        update_orbital_state();
+        recalculate_view_matrix();
+    }
+
+    void Camera::update_orbital_state()
+    {
+        m_target = glm::vec3(0.0f, 0.0f, 0.0f);
+        if (m_dragging || m_panning) 
+        {
+            m_moving = true;
+        } 
+        else 
+        {
+            m_moving = false;
+        }
+    }
 }
diff --git a/src/core/camera.h b/src/core/camera.h
index 25f7e2a..7ea5472 100644
--- a/src/core/camera.h
+++ b/src/core/camera.h
@@ -2,9 +2,21 @@
 
 #include <glm/glm.hpp>
 #include <glm/gtc/matrix_transform.hpp>
+#include <GLFW/glfw3.h>
+
+#define _USE_MATH_DEFINES
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
 
 namespace Donut
 {
+    enum class CameraMode
+    {
+        FPS,
+        Orbital
+    };
+
     class Camera
     {
     public:
@@ -42,10 +54,51 @@ namespace Donut
         void set_movement_speed(float speed) { m_movement_speed = speed;   }
         float get_movement_speed()    const  { return m_movement_speed;    }
 
+        void set_orbital_mode(bool enabled);
+        bool is_orbital_mode() const { return m_camera_mode == CameraMode::Orbital; }
+        
+        void set_target(const glm::vec3& target) { m_target = target; }
+        const glm::vec3& get_target() const { return m_target; }
+        
+        void set_radius(double radius) { m_radius = radius; }
+        double get_radius() const { return m_radius; }
+        
+        void set_min_radius(double min_radius) { m_min_radius = min_radius; }
+        double get_min_radius() const { return m_min_radius; }
+        
+        void set_max_radius(double max_radius) { m_max_radius = max_radius; }
+        double get_max_radius() const { return m_max_radius; }
+        
+        void set_azimuth(float azimuth) { m_azimuth = azimuth; }
+        float get_azimuth() const { return m_azimuth; }
+        
+        void set_elevation(float elevation) { m_elevation = elevation; }
+        float get_elevation() const { return m_elevation; }
+        
+        void set_orbit_speed(float orbit_speed) { m_orbit_speed = orbit_speed; }
+        float get_orbit_speed() const { return m_orbit_speed; }
+        
+        void set_zoom_speed(double zoom_speed) { m_zoom_speed = zoom_speed; }
+        double get_zoom_speed() const { return m_zoom_speed; }
+        
+        glm::vec3 get_orbital_position() const;
+        
+        void process_orbital_mouse_move(double x, double y);
+        void process_orbital_mouse_button(int button, int action, int mods);
+        void process_orbital_scroll(double x_offset, double y_offset);
+        
+        bool is_dragging() const { return m_dragging; }
+        bool is_panning() const { return m_panning; }
+        bool is_moving() const { return m_moving; }
+
     private:
         void recalculate_view_matrix();
         void recalculate_projection_matrix();
+        void update_orbital_state();
+
     private:
+        CameraMode m_camera_mode = CameraMode::FPS;
+
         glm::mat4 m_projection_matrix;
         glm::mat4 m_view_matrix;
         glm::mat4 m_view_projection_matrix;
@@ -63,5 +116,19 @@ namespace Donut
         bool  m_first_mouse       = true;
         float m_last_x            = 0.0f;
         float m_last_y            = 0.0f;
+
+        glm::vec3 m_target = glm::vec3(0.0f, 0.0f, 0.0f);
+        double m_radius = 6.34194e10;
+        double m_min_radius = 1e10;
+        double m_max_radius = 1e12;
+        float m_azimuth = 0.0f;
+        float m_elevation = static_cast<float>(M_PI) / 2.0f;
+        float m_orbit_speed = 0.01f;
+        double m_zoom_speed = 25e9f;
+        bool m_dragging = false;
+        bool m_panning = false;
+        bool m_moving = false;
+        double m_orbital_last_x = 0.0;
+        double m_orbital_last_y = 0.0;
     };
 }
diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
new file mode 100644
index 0000000..29fa65a
--- /dev/null
+++ b/src/engine/engine.cpp
@@ -0,0 +1,347 @@
+#include "engine.h"
+#include <GLFW/glfw3.h>
+#include <glad/glad.h>
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <limits>
+#include "rendering/vertex_buffer.h"
+#include "rendering/index_buffer.h"
+
+namespace Donut
+{
+    Engine::Engine() 
+        : m_sag_a(glm::vec3(0.0f, 0.0f, 0.0f), 
+          static_cast<float>(8.54e36)) 
+    {
+        GLFWwindow* window = static_cast<GLFWwindow*>(Application::get().get_window().get_native_window());
+        glfwGetFramebufferSize(window, &m_width, &m_height);
+        m_compute_height = 420;
+        m_compute_width = (m_width * 420) / m_height;
+        
+        m_camera.set_orbital_mode(true);
+        m_camera.set_radius(6.34194e10);
+        m_camera.set_min_radius(1e10);
+        m_camera.set_max_radius(1e12);
+        m_camera.set_orbit_speed(0.01f);
+        m_camera.set_zoom_speed(25e9f);
+        
+        m_objects = 
+        {
+            { glm::vec4(4e11f, 0.0f, 0.0f, 4e10f), glm::vec4(1,1,0,1), static_cast<float>(1.98892e30) },
+            { glm::vec4(0.0f, 0.0f, 4e11f, 4e10f), glm::vec4(1,0,0,1), static_cast<float>(1.98892e30) },
+            { glm::vec4(0.0f, 0.0f, 0.0f, m_sag_a.m_rs), glm::vec4(0,0,0,1), static_cast<float>(m_sag_a.m_mass) }
+        };
+
+        m_quad_shader    = Shader::create("assets/shaders/quad.glsl");
+        m_grid_shader    = Shader::create("assets/shaders/grid.glsl");
+        m_compute_shader = Shader::create_compute("Geodesic", load_compute_shader("assets/shaders/geodesic.glsl"));
+        
+        m_camera_ubo = UniformBuffer::create(128, 1);
+        m_disk_ubo = UniformBuffer::create(sizeof(float) * 4, 2);
+        
+        uint32_t obj_ubo_size = sizeof(int) + 3 * sizeof(float)
+            + 16 * (sizeof(glm::vec4) + sizeof(glm::vec4))
+            + 16 * sizeof(float);
+        m_objects_ubo = UniformBuffer::create(obj_ubo_size, 3);
+
+        float quad_vertices[] = 
+        {
+            -1.0f,  1.0f,  0.0f, 1.0f,
+            -1.0f, -1.0f,  0.0f, 0.0f,
+             1.0f, -1.0f,  1.0f, 0.0f,
+            
+            -1.0f,  1.0f,  0.0f, 1.0f,
+             1.0f, -1.0f,  1.0f, 0.0f,
+             1.0f,  1.0f,  1.0f, 1.0f
+        };
+
+        m_quad_vao = VertexArray::create();
+        
+        auto vertex_buffer = VertexBuffer::create(quad_vertices, static_cast<uint32_t>(sizeof(quad_vertices)));
+        VertexBufferLayout layout;
+        layout.push<float>(2);
+        layout.push<float>(2);
+        vertex_buffer->set_layout(layout);
+        m_quad_vao->add_vertex_buffer(vertex_buffer);
+
+        m_texture = Texture2D::create(m_width, m_height);
+    }
+
+    void Engine::generate_grid(const std::vector<ObjectData>& objects) 
+    {
+        const int grid_size = 25;
+        const float spacing = 1e10f;
+
+        std::vector<glm::vec3> vertices;
+        std::vector<uint32_t> indices;
+
+        for (int z = 0; z <= grid_size; ++z) 
+        {
+            for (int x = 0; x <= grid_size; ++x) 
+            {
+                float world_x = (x - grid_size / 2) * spacing;
+                float world_z = (z - grid_size / 2) * spacing;
+                float y = 0.0f;
+
+                for (const auto& obj : objects) 
+                {
+                    glm::vec3 obj_pos = glm::vec3(obj.m_pos_radius);
+                    double mass = obj.m_mass;
+                    double radius = obj.m_pos_radius.w;
+
+                    double r_s = 2.0 * G * mass / (c * c);
+                    double dx = world_x - obj_pos.x;
+                    double dz = world_z - obj_pos.z;
+                    double dist = sqrt(dx * dx + dz * dz);
+
+                    if (dist > r_s) 
+                    {
+                        double delta_y = 2.0 * sqrt(r_s * (dist - r_s));
+                        y += static_cast<float>(delta_y) - 3e10f;
+                    } 
+                    else 
+                    {
+                        y += 2.0f * static_cast<float>(sqrt(r_s * r_s)) - 3e10f;
+                    }
+                }
+
+                vertices.emplace_back(world_x, y, world_z);
+            }
+        }
+
+        for (int z = 0; z < grid_size; ++z) 
+        {
+            for (int x = 0; x < grid_size; ++x) 
+            {
+                int i = z * (grid_size + 1) + x;
+                indices.push_back(i);
+                indices.push_back(i + 1);
+                indices.push_back(i);
+                indices.push_back(i + grid_size + 1);
+            }
+        }
+
+        if (!m_grid_vao)
+        {
+            m_grid_vao = Ref<VertexArray>(VertexArray::create());
+            
+            auto vertex_buffer = Ref<VertexBuffer>(VertexBuffer::create(vertices.data(), static_cast<uint32_t>(vertices.size() * sizeof(glm::vec3))));
+            VertexBufferLayout layout;
+            layout.push<float>(3);
+            vertex_buffer->set_layout(layout);
+            m_grid_vao->add_vertex_buffer(vertex_buffer);
+
+            auto index_buffer = Ref<IndexBuffer>(IndexBuffer::create(indices.data(), static_cast<uint32_t>(indices.size())));
+            m_grid_vao->set_index_buffer(index_buffer);
+        }
+        else
+        {
+            auto vertex_buffer = m_grid_vao->get_vertex_buffers()[0];
+            vertex_buffer->set_data(vertices.data(), static_cast<uint32_t>(vertices.size() * sizeof(glm::vec3)));
+        }
+
+        m_grid_index_count = static_cast<int>(indices.size());
+    }
+
+    void Engine::draw_grid(const glm::mat4& view_proj) 
+    {
+        if (!m_grid_shader || !m_grid_vao) 
+            return;
+        
+        m_grid_shader->bind();
+        m_grid_shader->set_mat4("viewProj", view_proj);
+        
+        RenderCommand::disable_depth_test();
+        RenderCommand::enable_blending();
+        
+        m_grid_vao->bind();
+        glDrawElements(GL_LINES, m_grid_index_count, GL_UNSIGNED_INT, nullptr);
+        
+        RenderCommand::enable_depth_test();
+    }
+
+    void Engine::update_window_dimensions() 
+    {
+        GLFWwindow* window = static_cast<GLFWwindow*>(Application::get().get_window().get_native_window());
+        int old_width = m_width;
+        int old_height = m_height;
+        glfwGetFramebufferSize(window, &m_width, &m_height);
+        m_compute_height = 420;
+        m_compute_width = (m_width * 420) / m_height;
+        
+        if (old_width != m_width || old_height != m_height)
+            m_texture = Texture2D::create(m_width, m_height);
+    }
+
+    void Engine::draw_full_screen_quad() 
+    {
+        RenderCommand::set_viewport(0, 0, m_width, m_height);
+        
+        m_quad_shader->bind();
+        std::cout << "Texture ID: " << m_texture->get_renderer_id() << ", Size: " << m_texture->get_width() << "x" << m_texture->get_height() << std::endl;
+        m_texture->bind(0);
+        m_quad_shader->set_int("screenTexture", 0);
+        std::cout << "Set screenTexture uniform to slot 0\n";
+
+        RenderCommand::disable_depth_test();
+        RenderCommand::draw_indexed(m_quad_vao, 6);
+        RenderCommand::enable_depth_test();
+    }
+
+    void Engine::dispatch_compute(const Camera& cam) 
+    {
+        int cw = m_compute_width;
+        int ch = m_compute_height;
+
+        if (m_texture->get_width() != cw || m_texture->get_height() != ch) 
+            m_texture = Texture2D::create(cw, ch);
+
+        m_compute_shader->bind();
+        upload_camera_ubo(cam);
+        upload_disk_ubo();
+        upload_objects_ubo(m_objects);
+
+        m_texture->bind_as_image(0, false);
+
+        uint32_t groups_x = (uint32_t)std::ceil(cw / 16.0f);
+        uint32_t groups_y = (uint32_t)std::ceil(ch / 16.0f);
+        m_compute_shader->dispatch(groups_x, groups_y, 1);
+        m_compute_shader->memory_barrier(IMAGE_ACCESS_BARRIER_BIT);
+        
+        glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
+        glMemoryBarrier(GL_TEXTURE_FETCH_BARRIER_BIT);
+    }
+
+    void Engine::upload_camera_ubo(const Camera& cam) 
+    {
+        struct UBOData 
+        {
+            glm::vec3 pos; float _pad0;
+            glm::vec3 right; float _pad1;
+            glm::vec3 up; float _pad2;
+            glm::vec3 forward; float _pad3;
+            float tan_half_fov;
+            float aspect;
+            bool moving;
+            int _pad4;
+        } data;
+
+        glm::vec3 fwd = glm::normalize(cam.get_target() - cam.get_orbital_position());
+        glm::vec3 up = glm::vec3(0, 1, 0);
+        glm::vec3 right = glm::normalize(glm::cross(fwd, up));
+        up = glm::cross(right, fwd);
+
+        data.pos = cam.get_orbital_position();
+        data.right = right;
+        data.up = up;
+        data.forward = fwd;
+        data.tan_half_fov = static_cast<float>(tan(glm::radians(60.0f * 0.5f)));
+        data.aspect = static_cast<float>(m_width) / static_cast<float>(m_height);
+        data.moving = cam.is_dragging() || cam.is_panning();
+
+        m_camera_ubo->set_data(&data, sizeof(UBOData));
+    }
+
+    void Engine::upload_objects_ubo(const std::vector<ObjectData>& objs) 
+    {
+        struct UBOData 
+        {
+            int num_objects;
+            float _pad0, _pad1, _pad2;
+            glm::vec4 pos_radius[16];
+            glm::vec4 color[16];
+            float mass[16];
+        } data;
+
+        size_t count = std::min(objs.size(), size_t(16));
+        data.num_objects = static_cast<int>(count);
+
+        for (size_t i = 0; i < count; ++i) 
+        {
+            data.pos_radius[i] = objs[i].m_pos_radius;
+            data.color[i] = objs[i].m_color;
+            data.mass[i] = objs[i].m_mass;
+        }
+
+        m_objects_ubo->set_data(&data, sizeof(data));
+    }
+
+    void Engine::upload_disk_ubo() 
+    {
+        float r1 = static_cast<float>(m_sag_a.m_rs * 2.2);
+        float r2 = static_cast<float>(m_sag_a.m_rs * 5.2);
+        float num = 2.0f;
+        float thickness = 1e9f;
+        float disk_data[4] = { r1, r2, num, thickness };
+
+        m_disk_ubo->set_data(disk_data, sizeof(disk_data));
+    }
+
+    void Engine::update_physics(float delta_time) 
+    {
+        for (auto& obj : m_objects) 
+        {
+            for (auto& obj2 : m_objects) 
+            {
+                if (&obj == &obj2) continue;
+                float dx = obj2.m_pos_radius.x - obj.m_pos_radius.x;
+                float dy = obj2.m_pos_radius.y - obj.m_pos_radius.y;
+                float dz = obj2.m_pos_radius.z - obj.m_pos_radius.z;
+                float distance = sqrt(dx * dx + dy * dy + dz * dz);
+
+                if (distance > 0) 
+                {
+                    std::vector<double> direction = {dx / distance, dy / distance, dz / distance};
+                    double Gforce = (G * obj.m_mass * obj2.m_mass) / (distance * distance);
+                    double acc1 = Gforce / obj.m_mass;
+                    std::vector<double> acc = {direction[0] * acc1, direction[1] * acc1, direction[2] * acc1};
+
+                    if (m_gravity) 
+                    {
+                        obj.m_velocity.x += static_cast<float>(acc[0]);
+                        obj.m_velocity.y += static_cast<float>(acc[1]);
+                        obj.m_velocity.z += static_cast<float>(acc[2]);
+
+                        obj.m_pos_radius.x += static_cast<float>(obj.m_velocity.x);
+                        obj.m_pos_radius.y += static_cast<float>(obj.m_velocity.y);
+                        obj.m_pos_radius.z += static_cast<float>(obj.m_velocity.z);
+                    }
+                }
+            }
+        }
+    }
+
+    void Engine::render_scene()
+    {
+        glm::mat4 view = glm::lookAt(m_camera.get_orbital_position(), m_camera.get_target(), glm::vec3(0,1,0));
+        glm::mat4 proj = glm::perspective(glm::radians(60.0f), float(m_width)/m_height, 1e9f, 1e14f);
+        glm::mat4 view_proj = proj * view;
+        
+        generate_grid(m_objects);
+        draw_grid(view_proj);
+        
+        RenderCommand::set_viewport(0, 0, m_width, m_height);
+        dispatch_compute(m_camera);
+        draw_full_screen_quad();
+    }
+
+    std::string Engine::load_compute_shader(const std::string& path)
+    {
+        std::ifstream in(path);
+        if(!in.is_open()) 
+        {
+            std::cerr << "Failed to open compute shader: " << path << "\n";
+            return "";
+        }
+
+        std::stringstream ss;
+        ss << in.rdbuf();
+        std::string result = ss.str();
+        if (result.empty()) 
+            std::cerr << "Warning: Compute shader file is empty: " << path << "\n";
+        else 
+            std::cout << "Successfully loaded compute shader: " << path << " (size: " << result.size() << " bytes)\n";
+        return result;
+    }
+}
diff --git a/src/engine/engine.h b/src/engine/engine.h
new file mode 100644
index 0000000..6f90efb
--- /dev/null
+++ b/src/engine/engine.h
@@ -0,0 +1,118 @@
+#pragma once
+
+#include <vector>
+#include <iostream>
+#include <GLFW/glfw3.h>
+#include <glm/glm.hpp>
+#include <glm/gtc/matrix_transform.hpp>
+#include <glm/gtc/type_ptr.hpp>
+#include <fstream>
+#include <sstream>
+#include <chrono>
+#include <cmath>
+
+#include "core/application.h"
+#include "core/camera.h"
+#include "rendering/renderer.h"
+#include "rendering/shader.h"
+#include "rendering/texture.h"
+#include "rendering/vertex_array.h"
+#include "rendering/uniform_buffer.h"
+
+namespace Donut
+{
+    const double c = 299792458.0;
+    const double G = 6.67430e-11;
+
+    struct BlackHole 
+    {
+        glm::vec3 m_position;
+        double m_mass;
+        double m_radius;
+        double m_rs;
+
+        BlackHole(glm::vec3 pos, float mass) 
+            : m_position(pos),
+              m_mass(mass) 
+        {
+            m_rs = 2.0 * G * m_mass / (c * c);
+        }
+
+        bool intercept(float px, float py, float pz) const 
+        {
+            double dx = double(px) - double(m_position.x);
+            double dy = double(py) - double(m_position.y);
+            double dz = double(pz) - double(m_position.z);
+            double dist2 = dx * dx + dy * dy + dz * dz;
+            return dist2 < m_rs * m_rs;
+        }
+    };
+
+    struct ObjectData 
+    {
+        glm::vec4 m_pos_radius;
+        glm::vec4 m_color;
+        float m_mass;
+        glm::vec3 m_velocity = glm::vec3(0.0f, 0.0f, 0.0f);
+    };
+
+    class Engine
+    {
+    public:
+        Engine();
+        ~Engine() = default;
+
+        void generate_grid(const std::vector<ObjectData>& objects);
+        void draw_grid(const glm::mat4& view_proj);
+        void draw_full_screen_quad();
+        void dispatch_compute(const Camera& cam);
+        void upload_camera_ubo(const Camera& cam);
+        void upload_objects_ubo(const std::vector<ObjectData>& objs);
+        void upload_disk_ubo();
+        void render_scene();
+        void update_physics(float delta_time);
+        void update_window_dimensions();
+
+              Camera& get_camera()       { return m_camera; }
+        const Camera& get_camera() const { return m_camera; }
+        
+        const std::vector<ObjectData>& get_objects() const { return m_objects; }
+              std::vector<ObjectData>& get_objects()       { return m_objects; }
+        
+        bool get_gravity() const       { return m_gravity;    }
+        void set_gravity(bool gravity) { m_gravity = gravity; }
+        
+        int get_width()         const { return m_width;         }
+        int get_height()        const { return m_height;        }
+        int get_compute_width()  const { return m_compute_width;  }
+        int get_compute_height() const { return m_compute_height; }
+
+    private:
+        std::string create_basic_vertex_shader();
+        std::string create_basic_fragment_shader();
+        std::string load_compute_shader(const std::string& path);
+    private:
+        Ref<Shader>        m_grid_shader;
+        Ref<Shader>        m_quad_shader;
+        Ref<Shader>        m_compute_shader;
+        Ref<Texture2D>     m_texture;
+        Ref<VertexArray>   m_quad_vao;
+        Ref<VertexArray>   m_grid_vao;
+        Ref<UniformBuffer> m_camera_ubo;
+        Ref<UniformBuffer> m_disk_ubo;
+        Ref<UniformBuffer> m_objects_ubo;
+        
+        int   m_grid_index_count = 0;
+        int   m_width;
+        int   m_height;
+        int   m_compute_width;
+        int   m_compute_height;
+        float m_width_scale = 100000000000.0f;
+        float m_height_scale = 75000000000.0f;
+
+        std::vector<ObjectData> m_objects;
+        BlackHole               m_sag_a;
+        Camera                  m_camera;
+        bool                    m_gravity = false;
+    };
+}
diff --git a/src/engine/object.cpp b/src/engine/object.cpp
new file mode 100644
index 0000000..2e76b16
--- /dev/null
+++ b/src/engine/object.cpp
@@ -0,0 +1,46 @@
+#include "object.h"
+
+namespace Donut
+{
+    Ray::Ray(glm::vec3 o, glm::vec3 d) 
+        : m_origin(o), 
+          m_direction(glm::normalize(d)) { }
+
+    Material::Material(glm::vec3 c, float s, float e)
+        : m_color(c), 
+          m_specular(s), 
+          m_emission(e) { }
+
+    Object::Object(glm::vec3 c, float r, Material m) 
+        : m_centre(c), 
+          m_radius(r), 
+          m_material(m) { }
+
+    bool Object::intersect(Ray &ray, float &t)
+    {
+        glm::vec3 oc = ray.m_origin - m_centre;
+        float a = glm::dot(ray.m_direction, ray.m_direction); 
+        float b = 2.0f * glm::dot(oc, ray.m_direction);
+        float c = glm::dot(oc, oc) - m_radius * m_radius;
+        double discriminant = b*b - 4*a*c;
+
+        if(discriminant < 0)
+            return false;
+
+        float intercept = (-b - sqrt(discriminant)) / (2.0f*a);
+        if(intercept < 0)
+        {
+            intercept = (-b + sqrt(discriminant)) / (2.0f*a);
+            if(intercept<0)
+                return false;
+        }
+
+        t = intercept;
+        return true;
+    }
+
+    glm::vec3 Object::get_normal(glm::vec3 &point) const
+    {
+        return glm::normalize(point - m_centre);
+    }
+}
diff --git a/src/engine/object.h b/src/engine/object.h
new file mode 100644
index 0000000..5f5d86f
--- /dev/null
+++ b/src/engine/object.h
@@ -0,0 +1,38 @@
+#pragma once
+
+#include <glm/glm.hpp>
+
+namespace Donut
+{
+    class Ray
+    {
+    public:
+        glm::vec3 m_direction;
+        glm::vec3 m_origin;
+
+        Ray(glm::vec3 o, glm::vec3 d);
+    };
+
+    class Material
+    {
+    public:
+        glm::vec3 m_color;
+        float     m_specular;
+        float     m_emission;
+
+        Material(glm::vec3 c, float s, float e);
+    };
+
+    class Object
+    {
+    public:
+        glm::vec3 m_centre;
+        float     m_radius;
+        Material  m_material;
+    
+        Object(glm::vec3 c, float r, Material m);
+    
+        bool intersect(Ray &ray, float &t);
+        glm::vec3 get_normal(glm::vec3 &point) const;
+    };
+};
diff --git a/src/engine/scene.cpp b/src/engine/scene.cpp
new file mode 100644
index 0000000..bfac1aa
--- /dev/null
+++ b/src/engine/scene.cpp
@@ -0,0 +1,57 @@
+#include "scene.h"
+
+namespace Donut
+{
+    Scene::Scene() 
+        : m_light_pos(5.0f, 5.0f, 5.0f) { }
+
+    glm::vec3 Scene::trace(Ray &ray)
+    {
+        float closest = std::numeric_limits<float>::infinity();
+        const Object* hit_obj = nullptr;
+
+        for(auto& obj : objs)
+        {
+            float t;
+
+            if(obj.intersect(ray, t))
+                if(t < closest) 
+                {
+                    closest = t;
+                    hit_obj = &obj;
+                }
+        }
+        
+        if(hit_obj)
+        {
+            glm::vec3 hit_point = ray.m_origin + ray.m_direction * closest;
+            glm::vec3 normal = hit_obj->get_normal(hit_point);
+            glm::vec3 light_dir = glm::normalize(m_light_pos - hit_point);
+
+            float diff = std::max(glm::dot(normal, light_dir), 0.0f);
+
+            Ray shadow_ray(hit_point + normal * 0.001f, light_dir);
+            bool in_shadow = false;
+            
+            for(auto& obj : objs) 
+            {
+                float t;
+
+                if(obj.intersect(shadow_ray, t)) 
+                {
+                    in_shadow = true;
+                    break;
+                }
+            }
+
+            glm::vec3 color = hit_obj->m_material.m_color;
+            float ambient = 0.1f;
+
+            if (in_shadow) 
+                return color * ambient;
+            return color * (ambient + diff * 0.9f);
+        }
+
+        return glm::vec3(0.0f, 0.0f, 0.1f); 
+    }
+}
diff --git a/src/engine/scene.h b/src/engine/scene.h
new file mode 100644
index 0000000..abe582e
--- /dev/null
+++ b/src/engine/scene.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <vector>
+#include <limits>
+#include <glm/glm.hpp>
+
+#include "object.h"
+
+namespace Donut
+{
+    class Scene 
+    {
+    public:
+        std::vector<Object> objs;
+        glm::vec3 m_light_pos;
+
+        Scene();
+        glm::vec3 trace(Ray &ray);
+    };
+};
diff --git a/src/platform/opengl/opengl_renderer_api.cpp b/src/platform/opengl/opengl_renderer_api.cpp
index 4542231..628c0af 100644
--- a/src/platform/opengl/opengl_renderer_api.cpp
+++ b/src/platform/opengl/opengl_renderer_api.cpp
@@ -49,6 +49,11 @@ namespace Donut
         glEnable(GL_DEPTH_TEST);
     }
 
+    void OpenGLRendererAPI::disable_depth_test()
+    {
+        glDisable(GL_DEPTH_TEST);
+    }
+
     void OpenGLRendererAPI::set_face_culling(bool enabled)
     {
         if (enabled)
@@ -61,6 +66,17 @@ namespace Donut
             glDisable(GL_CULL_FACE);
     }
 
+    void OpenGLRendererAPI::enable_blending()
+    {
+        glEnable(GL_BLEND);
+        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    }
+
+    void OpenGLRendererAPI::disable_blending()
+    {
+        glDisable(GL_BLEND);
+    }
+
     void OpenGLRendererAPI::draw_indexed(const Ref<VertexArray>& vertex_array, uint32_t index_count)
     {
         uint32_t count = index_count ? index_count : vertex_array->get_index_buffer()->get_count();
diff --git a/src/platform/opengl/opengl_renderer_api.h b/src/platform/opengl/opengl_renderer_api.h
index 25accbb..fd446c6 100644
--- a/src/platform/opengl/opengl_renderer_api.h
+++ b/src/platform/opengl/opengl_renderer_api.h
@@ -19,7 +19,10 @@ namespace Donut
         virtual void set_clear_color(const glm::vec4& color)        override;
         virtual void clear()                                      override;
         virtual void enable_depth_test()                            override;
+        virtual void disable_depth_test() override;
         virtual void set_face_culling(bool enabled)                 override;
+        virtual void enable_blending() override;
+        virtual void disable_blending() override;
 
         virtual void draw_indexed(const Ref<VertexArray>& vertex_array, 
                                  uint32_t index_count = 0)         override;
diff --git a/src/platform/opengl/opengl_uniform_buffer.cpp b/src/platform/opengl/opengl_uniform_buffer.cpp
new file mode 100644
index 0000000..ca7d3d2
--- /dev/null
+++ b/src/platform/opengl/opengl_uniform_buffer.cpp
@@ -0,0 +1,29 @@
+#include "opengl_uniform_buffer.h"
+
+namespace Donut
+{
+    OpenGLUniformBuffer::OpenGLUniformBuffer(uint32_t size, uint32_t binding)
+        : m_size(size), m_binding(binding)
+    {
+        glGenBuffers(1, &m_renderer_id);
+        glBindBuffer(GL_UNIFORM_BUFFER, m_renderer_id);
+        glBufferData(GL_UNIFORM_BUFFER, size, nullptr, GL_DYNAMIC_DRAW);
+        glBindBufferBase(GL_UNIFORM_BUFFER, binding, m_renderer_id);
+    }
+
+    OpenGLUniformBuffer::~OpenGLUniformBuffer()
+    {
+        glDeleteBuffers(1, &m_renderer_id);
+    }
+
+    void OpenGLUniformBuffer::set_data(const void* data, uint32_t size, uint32_t offset)
+    {
+        glBindBuffer(GL_UNIFORM_BUFFER, m_renderer_id);
+        glBufferSubData(GL_UNIFORM_BUFFER, offset, size, data);
+    }
+
+    void OpenGLUniformBuffer::bind(uint32_t binding)
+    {
+        glBindBufferBase(GL_UNIFORM_BUFFER, binding, m_renderer_id);
+    }
+};
diff --git a/src/platform/opengl/opengl_uniform_buffer.h b/src/platform/opengl/opengl_uniform_buffer.h
new file mode 100644
index 0000000..2a9131f
--- /dev/null
+++ b/src/platform/opengl/opengl_uniform_buffer.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include "rendering/uniform_buffer.h"
+#include <glad/glad.h>
+
+namespace Donut
+{
+    class OpenGLUniformBuffer : public UniformBuffer
+    {
+    public:
+        OpenGLUniformBuffer(uint32_t size, uint32_t binding);
+        virtual ~OpenGLUniformBuffer();
+
+        virtual void set_data(const void* data, uint32_t size, uint32_t offset = 0) override;
+        virtual void bind(uint32_t binding) override;
+
+    private:
+        uint32_t m_renderer_id = 0;
+        uint32_t m_size = 0;
+        uint32_t m_binding = 0;
+    };
+};
diff --git a/src/platform/vulkan/vulkan_renderer_api.cpp b/src/platform/vulkan/vulkan_renderer_api.cpp
index f91a0ea..6273d31 100644
--- a/src/platform/vulkan/vulkan_renderer_api.cpp
+++ b/src/platform/vulkan/vulkan_renderer_api.cpp
@@ -22,10 +22,22 @@ namespace Donut
 	{
 	}
 
+	void VulkanRendererAPI::disable_depth_test()
+	{
+	}
+
 	void VulkanRendererAPI::set_face_culling(bool enabled)
 	{
 	}
 
+	void VulkanRendererAPI::enable_blending()
+	{
+	}
+
+	void VulkanRendererAPI::disable_blending()
+	{
+	}
+
 	void VulkanRendererAPI::draw_indexed(const Ref<VertexArray>& vertex_array, uint32_t index_count)
 	{
 	}
diff --git a/src/platform/vulkan/vulkan_renderer_api.h b/src/platform/vulkan/vulkan_renderer_api.h
index d1394b3..c0075a2 100644
--- a/src/platform/vulkan/vulkan_renderer_api.h
+++ b/src/platform/vulkan/vulkan_renderer_api.h
@@ -15,7 +15,10 @@ namespace Donut
 		virtual void set_clear_color(const glm::vec4& color)        override;
 		virtual void clear()                                      override;
 		virtual void enable_depth_test()                            override;
+		virtual void disable_depth_test()                           override;
 		virtual void set_face_culling(bool enabled)                 override;
+		virtual void enable_blending()                             override;
+		virtual void disable_blending()                            override;
 
 		virtual void draw_indexed(const Ref<VertexArray>& vertex_array, 
 								 uint32_t index_count = 0) override;
diff --git a/src/platform/vulkan/vulkan_uniform_buffer.cpp b/src/platform/vulkan/vulkan_uniform_buffer.cpp
new file mode 100644
index 0000000..6fafeee
--- /dev/null
+++ b/src/platform/vulkan/vulkan_uniform_buffer.cpp
@@ -0,0 +1,21 @@
+#include "vulkan_uniform_buffer.h"
+
+namespace Donut
+{
+    VulkanUniformBuffer::VulkanUniformBuffer(uint32_t size, uint32_t binding)
+        : m_size(size), m_binding(binding)
+    {
+    }
+
+    VulkanUniformBuffer::~VulkanUniformBuffer()
+    {
+    }
+
+    void VulkanUniformBuffer::set_data(const void* data, uint32_t size, uint32_t offset)
+    {
+    }
+
+    void VulkanUniformBuffer::bind(uint32_t binding)
+    {
+    }
+};
diff --git a/src/platform/vulkan/vulkan_uniform_buffer.h b/src/platform/vulkan/vulkan_uniform_buffer.h
new file mode 100644
index 0000000..e3c9196
--- /dev/null
+++ b/src/platform/vulkan/vulkan_uniform_buffer.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include "rendering/uniform_buffer.h"
+
+namespace Donut
+{
+    class VulkanUniformBuffer : public UniformBuffer
+    {
+    public:
+        VulkanUniformBuffer(uint32_t size, uint32_t binding);
+        virtual ~VulkanUniformBuffer();
+
+        virtual void set_data(const void* data, uint32_t size, uint32_t offset = 0) override;
+        virtual void bind(uint32_t binding) override;
+
+    private:
+        uint32_t m_size = 0;
+        uint32_t m_binding = 0;
+    };
+};
diff --git a/src/rendering/index_buffer.cpp b/src/rendering/index_buffer.cpp
index 1095e3b..3271a5a 100644
--- a/src/rendering/index_buffer.cpp
+++ b/src/rendering/index_buffer.cpp
@@ -6,14 +6,14 @@
 
 namespace Donut 
 {
-    IndexBuffer* IndexBuffer::create(const uint32_t* indices, uint32_t count) 
+    Ref<IndexBuffer> IndexBuffer::create(const uint32_t* indices, uint32_t count) 
     {
         switch (Renderer::get_api()) 
         {
             case RendererAPI::API::OpenGL:
-                return new OpenGLIndexBuffer(indices, count);
+                return create_ref<OpenGLIndexBuffer>(indices, count);
             case RendererAPI::API::Vulkan:
-                return new VulkanIndexBuffer((uint32_t*)indices, count);
+                return create_ref<VulkanIndexBuffer>((uint32_t*)indices, count);
             default:
                 return nullptr;
         }
diff --git a/src/rendering/index_buffer.h b/src/rendering/index_buffer.h
index 856559a..9859c20 100644
--- a/src/rendering/index_buffer.h
+++ b/src/rendering/index_buffer.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "core/memory.h"
 #include <cstdint>
 
 namespace Donut
@@ -13,6 +14,6 @@ namespace Donut
         virtual void     unbind()   const = 0;
         virtual uint32_t get_count() const = 0;
 
-        static IndexBuffer* create(const uint32_t* indices, uint32_t count);
+        static Ref<IndexBuffer> create(const uint32_t* indices, uint32_t count);
     };
 };
diff --git a/src/rendering/renderer.cpp b/src/rendering/renderer.cpp
index 5e4682c..f34e2b0 100644
--- a/src/rendering/renderer.cpp
+++ b/src/rendering/renderer.cpp
@@ -7,14 +7,14 @@
 
 namespace Donut 
 {
-    Scope<RendererAPI> RendererAPI::create()
+    Ref<RendererAPI> RendererAPI::create()
      {
         switch (s_api)
         {
             case API::OpenGL:
-                return create_scope<OpenGLRendererAPI>();
+                return create_ref<OpenGLRendererAPI>();
             case API::Vulkan:
-                return create_scope<VulkanRendererAPI>();
+                return create_ref<VulkanRendererAPI>();
             default:
                 return nullptr;
         }
@@ -50,7 +50,7 @@ namespace Donut
         RenderCommand::draw_indexed(vertex_array);
     }
 
-    Scope<RendererAPI> RenderCommand::s_renderer_api = RendererAPI::create();
+    Ref<RendererAPI> RenderCommand::s_renderer_api = RendererAPI::create();
 
     void Renderer::set_clear_color(const glm::vec4& color)
     {
diff --git a/src/rendering/renderer.h b/src/rendering/renderer.h
index 6212b21..4a028e5 100644
--- a/src/rendering/renderer.h
+++ b/src/rendering/renderer.h
@@ -26,14 +26,17 @@ namespace Donut
         virtual void set_clear_color(const glm::vec4& color)        = 0;
         virtual void clear()                                      = 0;
         virtual void enable_depth_test()                            = 0;
+        virtual void disable_depth_test()                           = 0;
         virtual void set_face_culling(bool enabled)                 = 0;
+        virtual void enable_blending()                             = 0;
+        virtual void disable_blending()                            = 0;
 
         virtual void draw_indexed(const Ref<VertexArray>& vertex_array, 
                                  uint32_t index_count = 0)         = 0;
 
         inline static API get_api()         { return s_api; }
         inline static void set_api(API api) { s_api = api;  }
-        static Scope<RendererAPI> create();
+        static Ref<RendererAPI> create();
     private:
         static API s_api;
     };
@@ -66,18 +69,33 @@ namespace Donut
             s_renderer_api->enable_depth_test();
         }
 
+        inline static void disable_depth_test()
+        {
+            s_renderer_api->disable_depth_test();
+        }
+
         inline static void set_face_culling(bool enabled)
         {
             s_renderer_api->set_face_culling(enabled);
         }
 
+        inline static void enable_blending()
+        {
+            s_renderer_api->enable_blending();
+        }
+
+        inline static void disable_blending()
+        {
+            s_renderer_api->disable_blending();
+        }
+
         inline static void draw_indexed(const Ref<VertexArray>& vertex_array, uint32_t index_count = 0)
         {
             s_renderer_api->draw_indexed(vertex_array, index_count);
         }
 
     private:
-        static Scope<RendererAPI> s_renderer_api;
+        static Ref<RendererAPI> s_renderer_api;
     };
 
     class Renderer 
diff --git a/src/rendering/shader.cpp b/src/rendering/shader.cpp
index 1bbd0fc..833b719 100644
--- a/src/rendering/shader.cpp
+++ b/src/rendering/shader.cpp
@@ -6,40 +6,40 @@
 
 namespace Donut
 {
-    Shader* Shader::create(const std::string& filepath) 
+    Ref<Shader> Shader::create(const std::string& filepath) 
     {
         switch (Renderer::get_api())
         {
             case RendererAPI::API::OpenGL:
-                return new OpenGLShader(filepath);
+                return create_ref<OpenGLShader>(filepath);
             case RendererAPI::API::Vulkan:
-                return new VulkanShader(filepath);
+                return create_ref<VulkanShader>(filepath);
             default:
                 return nullptr;
         }
     }
 
-    Shader* Shader::create(const std::string& name, const std::string& vertex_src, const std::string& fragment_src)
+    Ref<Shader> Shader::create(const std::string& name, const std::string& vertex_src, const std::string& fragment_src)
     {
         switch (Renderer::get_api()) 
         {
             case RendererAPI::API::OpenGL:
-                return new OpenGLShader(name, vertex_src, fragment_src);
+                return create_ref<OpenGLShader>(name, vertex_src, fragment_src);
             case RendererAPI::API::Vulkan:
-                return new VulkanShader(name, vertex_src, fragment_src);
+                return create_ref<VulkanShader>(name, vertex_src, fragment_src);
             default:
                 return nullptr;
         }
     }
 
-    Shader* Shader::create_compute(const std::string& name, const std::string& compute_src)
+    Ref<Shader> Shader::create_compute(const std::string& name, const std::string& compute_src)
     {
         switch (Renderer::get_api()) 
         {
             case RendererAPI::API::OpenGL:
-                return new OpenGLShader(name, compute_src);
+                return create_ref<OpenGLShader>(name, compute_src);
             case RendererAPI::API::Vulkan:
-                return new VulkanShader(name, compute_src);
+                return create_ref<VulkanShader>(name, compute_src);
             default:
                 return nullptr;
         }
@@ -58,14 +58,14 @@ namespace Donut
 
     Ref<Shader> ShaderLibrary::load(const std::string& filepath)
     {
-        auto shader = Ref<Shader>(Shader::create(filepath));
+        auto shader = Shader::create(filepath);
         add(shader);
         return shader;
     }
 
     Ref<Shader> ShaderLibrary::load(const std::string& name, const std::string& filepath)
     {
-        auto shader = Ref<Shader>(Shader::create(filepath));
+        auto shader = Shader::create(filepath);
         add(name, shader);
         return shader;
     }
diff --git a/src/rendering/shader.h b/src/rendering/shader.h
index 814f0cf..7f024bd 100644
--- a/src/rendering/shader.h
+++ b/src/rendering/shader.h
@@ -35,9 +35,9 @@ namespace Donut
 
         virtual const std::string& get_name() const = 0;
 
-        static Shader* create(const std::string& filepath);
-        static Shader* create(const std::string& name, const std::string& vertex_src, const std::string& fragment_src);
-        static Shader* create_compute(const std::string& name, const std::string& compute_src);
+        static Ref<Shader> create(const std::string& filepath);
+        static Ref<Shader> create(const std::string& name, const std::string& vertex_src, const std::string& fragment_src);
+        static Ref<Shader> create_compute(const std::string& name, const std::string& compute_src);
     };
 
     class ShaderLibrary
diff --git a/src/rendering/uniform_buffer.cpp b/src/rendering/uniform_buffer.cpp
new file mode 100644
index 0000000..4e693a2
--- /dev/null
+++ b/src/rendering/uniform_buffer.cpp
@@ -0,0 +1,23 @@
+#include "uniform_buffer.h"
+#include "renderer.h"
+
+#include "platform/opengl/opengl_uniform_buffer.h"
+#include "platform/vulkan/vulkan_uniform_buffer.h"
+
+namespace Donut
+{
+    Ref<UniformBuffer> UniformBuffer::create(uint32_t size, uint32_t binding)
+    {
+        switch (Renderer::get_api())
+        {
+        case RendererAPI::API::OpenGL:
+            return create_ref<OpenGLUniformBuffer>(size, binding);
+        case RendererAPI::API::Vulkan:
+            return create_ref<VulkanUniformBuffer>(size, binding);
+        case RendererAPI::API::None:
+            return nullptr;
+        default:
+            return nullptr;
+        }
+    }
+};
diff --git a/src/rendering/uniform_buffer.h b/src/rendering/uniform_buffer.h
new file mode 100644
index 0000000..4df39d9
--- /dev/null
+++ b/src/rendering/uniform_buffer.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include "core/memory.h"
+#include <cstdint>
+
+namespace Donut
+{
+    class UniformBuffer
+    {
+    public:
+        virtual ~UniformBuffer() = default;
+
+        virtual void set_data(const void* data, uint32_t size, uint32_t offset = 0) = 0;
+        virtual void bind(uint32_t binding) = 0;
+
+        static Ref<UniformBuffer> create(uint32_t size, uint32_t binding);
+    };
+};
diff --git a/src/rendering/vertex_array.cpp b/src/rendering/vertex_array.cpp
index bb92ff3..d0cd4b0 100644
--- a/src/rendering/vertex_array.cpp
+++ b/src/rendering/vertex_array.cpp
@@ -17,14 +17,14 @@ namespace Donut
         }
     }
 
-    VertexArray* VertexArray::create() 
+    Ref<VertexArray> VertexArray::create() 
     {
         switch (Renderer::get_api()) 
         {
             case RendererAPI::API::OpenGL:
-                return new OpenGLVertexArray();
+                return create_ref<OpenGLVertexArray>();
             case RendererAPI::API::Vulkan:
-                return new VulkanVertexArray();
+                return create_ref<VulkanVertexArray>();
             default:
                 return nullptr;
         }
diff --git a/src/rendering/vertex_array.h b/src/rendering/vertex_array.h
index a39849f..3729167 100644
--- a/src/rendering/vertex_array.h
+++ b/src/rendering/vertex_array.h
@@ -23,6 +23,6 @@ namespace Donut
         virtual const std::vector<Ref<VertexBuffer>>& get_vertex_buffers() const = 0;
         virtual const Ref<IndexBuffer>& get_index_buffer()                 const = 0;
 
-        static VertexArray* create();
+        static Ref<VertexArray> create();
     };
 };
diff --git a/src/rendering/vertex_buffer.cpp b/src/rendering/vertex_buffer.cpp
index 4929711..ef2b288 100644
--- a/src/rendering/vertex_buffer.cpp
+++ b/src/rendering/vertex_buffer.cpp
@@ -6,14 +6,14 @@
 
 namespace Donut
 {
-    VertexBuffer* VertexBuffer::create(const void* data, uint32_t size)
+    Ref<VertexBuffer> VertexBuffer::create(const void* data, uint32_t size)
     {
         switch (Renderer::get_api()) 
         {
             case RendererAPI::API::OpenGL:
-                return new OpenGLVertexBuffer(data, size);
+                return create_ref<OpenGLVertexBuffer>(data, size);
             case RendererAPI::API::Vulkan:
-                return new VulkanVertexBuffer((float*)data, size);
+                return create_ref<VulkanVertexBuffer>((float*)data, size);
             default:
                 return nullptr;
         }
diff --git a/src/rendering/vertex_buffer.h b/src/rendering/vertex_buffer.h
index 77a76c9..39f43ba 100644
--- a/src/rendering/vertex_buffer.h
+++ b/src/rendering/vertex_buffer.h
@@ -1,5 +1,7 @@
 #pragma once
 
+#include "core/memory.h"
+
 #include <cstdint>
 #include <vector>
 
@@ -22,7 +24,7 @@ namespace Donut
         ~VertexBufferLayout() = default;
 
         template<typename T>
-        void push(uint32_t count) 
+        void push(uint32_t count)
         {
             static_assert(false);
         }
@@ -68,6 +70,6 @@ namespace Donut
         virtual const VertexBufferLayout& get_layout()      const = 0;
         virtual void set_layout(const VertexBufferLayout& layout) = 0;
 
-        static VertexBuffer* create(const void* data, uint32_t size);
+        static Ref<VertexBuffer> create(const void* data, uint32_t size);
     };
 };
diff --git a/src/states/simulation_state.cpp b/src/states/simulation_state.cpp
index 7e9cb76..fc235ff 100644
--- a/src/states/simulation_state.cpp
+++ b/src/states/simulation_state.cpp
@@ -1,14 +1,18 @@
 #include "simulation_state.h"
 #include "rendering/renderer.h"
 #include "core/application.h"
+#include "core/window.h"
+#include "core/event.h"
 
 #include <imgui.h>
+#include <GLFW/glfw3.h>
 
 namespace Donut
 {
     void SimulationState::on_enter()
     {
         DONUT_INFO("Entering Simulation State");
+        m_initialized = true;
     }
     
     void SimulationState::on_exit()
@@ -18,23 +22,79 @@ namespace Donut
     
     void SimulationState::on_update(float delta_time)
     {
+        
+        m_engine.update_window_dimensions();
+        m_engine.update_physics(delta_time);
+        
+        if (m_engine.get_camera().is_dragging()) 
+        {
+            GLFWwindow* window = static_cast<GLFWwindow*>(Application::get().get_window().get_native_window());
+            double xpos, ypos;
+            glfwGetCursorPos(window, &xpos, &ypos);
+            m_engine.get_camera().process_orbital_mouse_move(xpos, ypos);
+        }
     }
     
     void SimulationState::on_render()
     {
-        Renderer::set_clear_color({ 0.0f, 0.0f, 0.0f, 1.0f });
-        Renderer::clear();
+        if (!m_initialized) return;
+        
+        RenderCommand::set_clear_color(glm::vec4(0.0f, 0.0f, 0.0f, 1.0f));
+        RenderCommand::clear();
+        
+        m_engine.generate_grid(m_engine.get_objects());
+        
+        glm::mat4 view = glm::lookAt(m_engine.get_camera().get_orbital_position(), m_engine.get_camera().get_target(), glm::vec3(0,1,0));
+        glm::mat4 proj = glm::perspective(glm::radians(60.0f), float(m_engine.get_width())/m_engine.get_height(), 1e9f, 1e14f);
+        glm::mat4 view_proj = proj * view;
+        
+        m_engine.draw_grid(view_proj);
+        
+        RenderCommand::set_viewport(0, 0, m_engine.get_width(), m_engine.get_height());
+        m_engine.dispatch_compute(m_engine.get_camera());
+        m_engine.draw_full_screen_quad();
     }
     
     void SimulationState::on_event(Event& event)
     {
+        if (!m_initialized) return;
+        
+        if (event.get_event_type() == EventType::MouseButtonPressed)
+        {
+            MouseButtonPressedEvent& e = (MouseButtonPressedEvent&)event;
+            int button = e.get_mouse_button();
+            
+            m_engine.get_camera().process_orbital_mouse_button(button, GLFW_PRESS, 0);
+        }
+        else if (event.get_event_type() == EventType::MouseButtonReleased)
+        {
+            MouseButtonReleasedEvent& e = (MouseButtonReleasedEvent&)event;
+            int button = e.get_mouse_button();
+            m_engine.get_camera().process_orbital_mouse_button(button, GLFW_RELEASE, 0);
+        }
+        
+        if (event.get_event_type() == EventType::MouseScrolled)
+        {
+            MouseScrolledEvent& e = (MouseScrolledEvent&)event;
+            m_engine.get_camera().process_orbital_scroll(e.get_x_offset(), e.get_y_offset());
+        }
+        
+        if (event.get_event_type() == EventType::KeyPressed)
+        {
+            KeyPressedEvent& e = (KeyPressedEvent&)event;
+            if (e.get_key_code() == GLFW_KEY_G)
+            {
+                m_engine.set_gravity(!m_engine.get_gravity());
+                DONUT_INFO("Gravity turned {}", m_engine.get_gravity() ? "ON" : "OFF");
+            }
+        }
     }
     
     void SimulationState::on_im_ui_render()
     {
         ImGui::Begin("Simulation Controls");
         
-        ImGui::Text("Simulation State");
+        ImGui::Text("Black Hole Simulation");
         if (ImGui::Button("Back to Config"))
             Application::get().get_state_manager().switch_to_state("Config");
 
@@ -43,6 +103,33 @@ namespace Donut
         ImGui::Text("Simulation Info:");
         ImGui::Text("FPS: %.1f", ImGui::GetIO().Framerate);
         ImGui::Text("Frame Time: %.3f ms", 1000.0f / ImGui::GetIO().Framerate);
+        ImGui::Text("Resolution: %dx%d", m_engine.get_width(), m_engine.get_height());
+        ImGui::Text("Compute Resolution: %dx%d", m_engine.get_compute_width(), m_engine.get_compute_height());
+        ImGui::Text("Objects: %zu", m_engine.get_objects().size());
+        
+        ImGui::Separator();
+        
+        ImGui::Text("Controls:");
+        ImGui::Text("Left Mouse: Orbit camera");
+        ImGui::Text("Scroll: Zoom in/out");
+        ImGui::Text("G: Toggle gravity");
+        ImGui::Text("Right Mouse: Enable gravity (hold)");
+        
+        ImGui::Separator();
+        
+        ImGui::Text("Physics:");
+        bool gravity = m_engine.get_gravity();
+        if (ImGui::Checkbox("Gravity Enabled", &gravity))
+            m_engine.set_gravity(gravity);
+        
+        ImGui::Text("Camera:");
+        ImGui::Text("Position: (%.2e, %.2e, %.2e)", 
+                   m_engine.get_camera().get_orbital_position().x, 
+                   m_engine.get_camera().get_orbital_position().y, 
+                   m_engine.get_camera().get_orbital_position().z);
+        ImGui::Text("Radius: %.2e", m_engine.get_camera().get_radius());
+        ImGui::Text("Azimuth: %.2f", m_engine.get_camera().get_azimuth());
+        ImGui::Text("Elevation: %.2f", m_engine.get_camera().get_elevation());
         
         ImGui::End();
     }
diff --git a/src/states/simulation_state.h b/src/states/simulation_state.h
index 4bb1c1b..68788e8 100644
--- a/src/states/simulation_state.h
+++ b/src/states/simulation_state.h
@@ -3,6 +3,8 @@
 #include "core/state.h"
 #include "core/event.h"
 #include "core/log.h"
+#include "engine/engine.h"
+#include <vector>
 
 namespace Donut
 {
@@ -18,5 +20,9 @@ namespace Donut
         void on_render()                override;
         void on_im_ui_render()            override;
         void on_event(Event& event)     override;
+    
+    private:
+        Engine m_engine;
+        bool   m_initialized = false;
     };
 };