diff --git a/src/1_model.glsl b/src/1_model.glsl
index 6d6fe6d..1af8dfe 100644
--- a/src/1_model.glsl
+++ b/src/1_model.glsl
@@ -26,18 +26,15 @@ mat4 model(bool is_moon, float time)
   // Based on:
   // https://www.opengl-tutorial.org/beginners-tutorials/tutorial-3-matrices/#cumulating-transformations
 
-  mat4 scale_matrix = uniform_scale(0.30);
-
   float r = 2.0;
-  mat4 translation_matrix = translate(vec3(r, 0, 0));
-
-  // TODO Why is PI not defined?
-  float full_rotation = 2 * 3.14159;
+  float full_rotation = 2 * M_PI;
   float theta = full_rotation * time / 4.0;
-  mat4 rotation_matrix = rotate_about_y(theta);
+  // Invert rotation
+  theta = -theta;
 
-  // Small hack to make the moon rotate around the origin
-  // Usually you would rotate first, then translate
-  return rotation_matrix * translation_matrix * scale_matrix;
+  float x = r * cos(theta);
+  float z = r * sin(theta);
+
+  return translate(vec3(x, 0, z)) * rotate_about_y(theta) * uniform_scale(0.30);
   /////////////////////////////////////////////////////////////////////////////
 }
diff --git a/src/2_tessellate_5.tcs b/src/2_tessellate_5.tcs
index ce569ee..bc6575b 100644
--- a/src/2_tessellate_5.tcs
+++ b/src/2_tessellate_5.tcs
@@ -14,7 +14,14 @@ void main()
 {   
   /////////////////////////////////////////////////////////////////////////////
   // Replace with your code:
-  pos_es_in[gl_InvocationID] = pos_cs_in[gl_InvocationID];
+    // Hard-code each tessellation level to 5
+    gl_TessLevelOuter[0] = 5;
+    gl_TessLevelOuter[1] = 5;
+    gl_TessLevelOuter[2] = 5;
+    gl_TessLevelInner[0] = 5;
+
+    // Pass through the input vertices
+    pos_es_in[gl_InvocationID] = pos_cs_in[gl_InvocationID];
   /////////////////////////////////////////////////////////////////////////////
 }
 
diff --git a/src/3_snap_to_sphere.tes b/src/3_snap_to_sphere.tes
index 873e025..0e2a1b6 100644
--- a/src/3_snap_to_sphere.tes
+++ b/src/3_snap_to_sphere.tes
@@ -35,10 +35,15 @@ void main()
   // (so before model, view, proj are applied)
   
   /////////////////////////////////////////////////////////////////////////////
-  // Replace with your code 
+  // Replace with your code
+  // Based on:
+  // https://learnopengl.com/Guest-Articles/2021/Tessellation/Tessellation
+  sphere_fs_in = normalize(interp_pos.xyz);
+  view_pos_fs_in = view * model(is_moon, animation_seconds) * vec4(sphere_fs_in, 1.0);
+  normal_fs_in = normalize(mat3(view * model(is_moon, animation_seconds)) * sphere_fs_in);
+  pos_fs_in = proj * view_pos_fs_in;
 
-
-  gl_Position = interp_pos;
+  gl_Position = pos_fs_in;
   /////////////////////////////////////////////////////////////////////////////
 }