diff --git a/src/shader/main_shader.c b/src/shader/main_shader.c
index ba70935..e7e4857 100644
--- a/src/shader/main_shader.c
+++ b/src/shader/main_shader.c
@@ -1,6 +1,7 @@
 #include "main_shader.h"
 #include "img.h"
 #include "obj.h"
+#include "render.h"
 #include "shader.h"
 #include "utils.h"
 #include "vec.h"
@@ -38,6 +39,15 @@ FragmentResult diffuse_shader_fragment(void *shader, const V3f *barycentric, con
   V3f normal   = mat3x3_mul_vec3(normal_mat, (*barycentric));
   V2f uv       = mat2x3_mul_vec3(uv_mat, (*barycentric));
 
+  V4f shadow_position_h = V3_to_V4(position);
+  shadow_position_h     = mat4x4_mul_vec4(shdr->shadow_matrix, shadow_position_h);
+  V3f shadow_position   = project_vec4(shadow_position_h);
+
+  // Calculate shadow
+  const Render *shadow_pass = &(g_render_passes[RENDER_PASS_SHADOW]);
+  f32 shadow_z              = get_pixel(f32, &(shadow_pass->depth), shadow_position.x, shadow_position.y);
+  f32 shadow                = 0.3f + 0.7f * (shadow_z < shadow_position.z + 10.0f);
+
 #pragma region darboux_frame_tangent_normals
   /**
    * Based on the following section of the tinyrenderer tutorial
@@ -96,9 +106,9 @@ FragmentResult diffuse_shader_fragment(void *shader, const V3f *barycentric, con
   f32 g         = clamp(intensity + shdr->ambient.g, 0.0f, 1.0f);
   f32 b         = clamp(intensity + shdr->ambient.b, 0.0f, 1.0f);
 
-  output.r *= r;
-  output.g *= g;
-  output.b *= b;
+  output.r *= r * shadow;
+  output.g *= g * shadow;
+  output.b *= b * shadow;
 
   return (FragmentResult){.colour = output};
 }