diff --git a/gloom-rs/shaders/simple.frag b/gloom-rs/shaders/simple.frag
index 9845402..35509b5 100644
--- a/gloom-rs/shaders/simple.frag
+++ b/gloom-rs/shaders/simple.frag
@@ -3,7 +3,10 @@
 in vec4 fragment_colors;
 out vec4 color;
 
+uint grid_size = 200;
+
 void main()
 {
-    color = fragment_colors;
+    float col = (1 - (int(gl_FragCoord.y) / grid_size % 2) - (int(gl_FragCoord.x)) / grid_size % 2) * 1.0f;
+    color = vec4(col, 0.0f, col, col);
 }