diff --git a/src/4_blinn_phong.glsl b/src/4_blinn_phong.glsl
index f2e3ef8..a40a3c8 100644
--- a/src/4_blinn_phong.glsl
+++ b/src/4_blinn_phong.glsl
@@ -2,7 +2,7 @@
 // surface and a light direction. Assume the light has a low
 // ambient intensity of 0.1. To avoid confusion: this Blinn-Phong shading model
 // should only consist of ambient, diffuse and specular lighting.
-// Do not divide by rē (the squared distance to the point light).
+// Do not divide by r^2 (the squared distance to the point light).
 
 // Inputs:
 //   ka  rgb ambient color
@@ -23,8 +23,18 @@ vec3 blinn_phong(
   vec3 l)
 {
   /////////////////////////////////////////////////////////////////////////////
-  // Replace with your code 
-  return vec3(1,1,1);
+  // Replace with your code
+  float AMBIENT_INTENSITY = 0.1;
+
+  /* Ambient lighting */
+  vec3 rgb = ka * AMBIENT_INTENSITY;
+  /* Diffuse component (Lambertian shading) */
+  rgb += kd * max(dot(n, l), 0.0);
+  /* Specular component (Blinn-Phong shading) */
+  vec3 h = normalize(v + l);
+  rgb += ks * pow(max(0.0, dot(n, h)), p);
+
+  return rgb;
   /////////////////////////////////////////////////////////////////////////////
 }
 
diff --git a/src/4_lit.fs b/src/4_lit.fs
index b08d514..8955a5d 100644
--- a/src/4_lit.fs
+++ b/src/4_lit.fs
@@ -23,7 +23,32 @@ out vec3 color;
 void main()
 {
   /////////////////////////////////////////////////////////////////////////////
-  // Replace with your code 
-  color = vec3(1,1,1);
+  // Replace with your code
+  float r = 10.0;
+  float h = 8.0;
+  float f = 8.0;
+  float p = 1000.0;
+
+  float x = r * cos(2.0 * M_PI * animation_seconds / f);
+  float z = r * sin(2.0 * M_PI * animation_seconds / f);
+  vec3 light_pos = vec3(x, h, z);
+
+  // Calculate the light direction
+  vec3 l = normalize(light_pos - sphere_fs_in);
+
+  // Calculate the view direction
+  vec3 v = normalize(view_pos_fs_in.xyz - sphere_fs_in);
+  v = normalize(-view_pos_fs_in.xyz);
+
+  // Calculate the normal direction
+  vec3 n = normalize(normal_fs_in);
+
+  // Base colors
+  vec3 ka = vec3(0.1, 0.1, 0.1); // Ambient color
+  vec3 kd = is_moon ? vec3(0.5, 0.45, 0.5) : vec3(0.2, 0.3, 0.8); // Diffuse color
+  vec3 ks = vec3(1.0, 1.0, 1.0); // Specular color
+
+  // Compute the Blinn-Phong shading
+  color = blinn_phong(ka, kd, ks, p, n, v, l);
   /////////////////////////////////////////////////////////////////////////////
 }