diff --git a/resources/shaders/doom.frag b/resources/shaders/doom.frag
index 4672c94..b8b609a 100644
--- a/resources/shaders/doom.frag
+++ b/resources/shaders/doom.frag
@@ -18,6 +18,15 @@ uniform float uHorizontalScale;
 uniform float uVerticalScale;
 uniform float uPixelSize;
 
+// This method returns a mask which smoothly transitions towards zero when approaching
+// the window's top or bottom border.
+float getEdgeMask(vec2 uv, float fadeWidth) {
+  float mask = 1.0;
+  mask *= smoothstep(0.0, 1.0, clamp(uv.y / fadeWidth, 0.0, 1.0));
+  mask *= smoothstep(0.0, 1.0, clamp((1.0 - uv.y) / fadeWidth, 0.0, 1.0));
+  return mask;
+}
+
 void main() {
   // We simply inverse the progress for opening windows.
   float pixelateProgress = uForOpening ? 0.9 - uProgress : uProgress;
@@ -47,5 +56,7 @@ void main() {
 
   vec4 oColor = getInputColor(texcoord);
 
+  oColor.a *= getEdgeMask(iTexCoord.st, 0.1);
+
   setOutputColor(oColor);
 }
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