diff --git a/src/shaders/main.wesl b/src/shaders/main.wesl
index 20d3c28..089e7c3 100644
--- a/src/shaders/main.wesl
+++ b/src/shaders/main.wesl
@@ -81,6 +81,15 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
     }
 }
 
+/// Fragment shader for transform gizmo lines.
+/// Outputs `world_normal` directly as the RGB color — the vertex data encodes
+/// axis color (X=red, Y=green, Z=blue) in the normal attribute rather than
+/// storing a true geometric normal.
+@fragment
+fn fs_gizmo(in: VertexOutput) -> @location(0) vec4<f32> {
+    return vec4(in.world_normal, 1.0);
+}
+
 @group(1) @binding(0)
 var heightmap_texture: texture_2d<f32>;