diff --git a/shader-test/source/CShader.f.glsl b/shader-test/source/CShader.f.glsl
index 7ad6aad..a0cd622 100644
--- a/shader-test/source/CShader.f.glsl
+++ b/shader-test/source/CShader.f.glsl
@@ -1,7 +1,9 @@
 #pragma header
 
+uniform bool invert = true;
+
 void main()
 {
     vec4 color = flixel_texture2D(bitmap, openfl_TextureCoordv);
-    gl_FragColor = vec4((1.0 - color.r) * color.a, (1.0 - color.g) * color.a, (1.0 - color.b) * color.a,   color.a);
+    gl_FragColor = invert ? vec4((1.0 - color.r) * color.a, (1.0 - color.g) * color.a, (1.0 - color.b) * color.a,   color.a) : color;
 }
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diff --git a/shader-test/source/PlayState.kiss b/shader-test/source/PlayState.kiss
index bbf87a7..82666d8 100644
--- a/shader-test/source/PlayState.kiss
+++ b/shader-test/source/PlayState.kiss
@@ -6,15 +6,22 @@
 
 (extends FlxState)
 
+(prop &mut shader null)
+
 (method &override :Void create []
     (super.create)
     (let [bg (new FlxSprite 0 0 "assets/images/apTestRoomEdited.jpg")]
         (bg.setGraphicSize FlxG.width FlxG.height)
         (bg.screenCenter)
         (add bg))
-    (let [:BitmapFilter filter (new ShaderFilter (new CShader))
+    (set shader (new CShader))
+    (set shader.data.invert.value [true])
+    (let [:BitmapFilter filter (new ShaderFilter shader)
             :Array<BitmapFilter> filters [filter]]
         (FlxG.camera.setFilters filters)))
 
 (method &override :Void update [:Float elapsed]
-    (super.update elapsed))
\ No newline at end of file
+    (super.update elapsed)
+
+    (when FlxG.keys.justPressed.SPACE
+        (set shader.data.invert.value [!(first shader.data.invert.value)])))
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