diff --git a/src/shader_manager.py b/src/shader_manager.py
index c403aa5..da535d9 100644
--- a/src/shader_manager.py
+++ b/src/shader_manager.py
@@ -4,6 +4,7 @@ class ShaderManager:
  def __init__(self):
   self.program = None
   self.bg_program = None
+  self.pp_program = None
 
  def compile_shader(self, vertex_src: str, fragment_src: str) -> int:
   program = gl.glCreateProgram()
@@ -98,3 +99,55 @@ void main() {
    gl.glUniform2f(u_res_loc, float(width), float(height))
   gl.glDrawArrays(gl.GL_TRIANGLE_STRIP, 0, 4)
   gl.glUseProgram(0)
+
+ def setup_post_process_shader(self):
+  vertex_src = """
+#version 330 core
+const vec2 positions[4] = vec2[](
+ vec2(-1.0, -1.0),
+ vec2( 1.0, -1.0),
+ vec2(-1.0,  1.0),
+ vec2( 1.0,  1.0)
+);
+const vec2 uvs[4] = vec2[](
+ vec2(0.0, 0.0),
+ vec2(1.0, 0.0),
+ vec2(0.0, 1.0),
+ vec2(1.0, 1.0)
+);
+out vec2 v_uv;
+void main() {
+ gl_Position = vec4(positions[gl_VertexID], 0.0, 1.0);
+ v_uv = uvs[gl_VertexID];
+}
+"""
+  fragment_src = """
+#version 330 core
+in vec2 v_uv;
+uniform sampler2D u_texture;
+uniform float u_time;
+out vec4 FragColor;
+void main() {
+ vec4 color = texture(u_texture, v_uv);
+ float scanline = sin(v_uv.y * 800.0 + u_time * 2.0) * 0.04;
+ color.rgb -= scanline;
+ FragColor = color;
+}
+"""
+  self.pp_program = self.compile_shader(vertex_src, fragment_src)
+
+ def render_post_process(self, texture_id, width, height, time):
+  if not self.pp_program:
+   return
+  gl.glUseProgram(self.pp_program)
+  gl.glActiveTexture(gl.GL_TEXTURE0)
+  gl.glBindTexture(gl.GL_TEXTURE_2D, texture_id)
+  u_tex_loc = gl.glGetUniformLocation(self.pp_program, "u_texture")
+  if u_tex_loc != -1:
+   gl.glUniform1i(u_tex_loc, 0)
+  u_time_loc = gl.glGetUniformLocation(self.pp_program, "u_time")
+  if u_time_loc != -1:
+   gl.glUniform1f(u_time_loc, float(time))
+  gl.glDrawArrays(gl.GL_TRIANGLE_STRIP, 0, 4)
+  gl.glBindTexture(gl.GL_TEXTURE_2D, 0)
+  gl.glUseProgram(0)
diff --git a/tests/test_post_process.py b/tests/test_post_process.py
new file mode 100644
index 0000000..16703a2
--- /dev/null
+++ b/tests/test_post_process.py
@@ -0,0 +1,53 @@
+import unittest
+from unittest.mock import MagicMock, patch
+import sys
+
+# Mock OpenGL.GL before importing ShaderManager
+gl_mock = MagicMock()
+# Setup some constants
+gl_mock.GL_VERTEX_SHADER = 0x8B31
+gl_mock.GL_FRAGMENT_SHADER = 0x8B30
+gl_mock.GL_COMPILE_STATUS = 0x8B81
+gl_mock.GL_LINK_STATUS = 0x8B82
+gl_mock.GL_TEXTURE0 = 0x84C0
+gl_mock.GL_TEXTURE_2D = 0x0DE1
+gl_mock.GL_TRIANGLE_STRIP = 0x0005
+
+opengl_mock = MagicMock()
+sys.modules['OpenGL'] = opengl_mock
+sys.modules['OpenGL.GL'] = gl_mock
+opengl_mock.GL = gl_mock
+
+from src.shader_manager import ShaderManager
+
+class TestPostProcess(unittest.TestCase):
+ def setUp(self):
+  gl_mock.reset_mock()
+  # Mock return values for shader compilation
+  gl_mock.glCreateProgram.return_value = 1
+  gl_mock.glCreateShader.return_value = 2
+  gl_mock.glGetShaderiv.return_value = 1 # GL_TRUE
+  gl_mock.glGetProgramiv.return_value = 1 # GL_TRUE
+  gl_mock.glGetUniformLocation.return_value = 10
+  
+ def test_setup_post_process_shader(self):
+  sm = ShaderManager()
+  sm.setup_post_process_shader()
+  self.assertEqual(sm.pp_program, 1)
+  gl_mock.glCreateProgram.assert_called()
+  gl_mock.glLinkProgram.assert_called_with(1)
+
+ def test_render_post_process(self):
+  sm = ShaderManager()
+  sm.pp_program = 1
+  sm.render_post_process(texture_id=5, width=800, height=600, time=1.0)
+  
+  gl_mock.glUseProgram.assert_any_call(1)
+  gl_mock.glActiveTexture.assert_called_with(gl_mock.GL_TEXTURE0)
+  gl_mock.glBindTexture.assert_any_call(gl_mock.GL_TEXTURE_2D, 5)
+  gl_mock.glUniform1f.assert_called()
+  gl_mock.glDrawArrays.assert_called_with(gl_mock.GL_TRIANGLE_STRIP, 0, 4)
+  gl_mock.glUseProgram.assert_any_call(0)
+
+if __name__ == '__main__':
+ unittest.main()