diff --git a/simple_sdf/shaders/SDF.frag b/simple_sdf/shaders/SDF.frag
index 31d9352d5..327222662 100644
--- a/simple_sdf/shaders/SDF.frag
+++ b/simple_sdf/shaders/SDF.frag
@@ -10,6 +10,26 @@ out vec4 fragColor;
 vec3 pink = vec3(255, 105, 180) / 255;
 
 // dot2 and sdHeart from https://iquilezles.org/articles/distfunctions2d/
+//
+// The MIT License
+// Copyright © 2015 Inigo Quilez
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions: The above copyright
+// notice and this permission notice shall be included in all copies or
+// substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS",
+// WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
+// THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+// https://www.youtube.com/c/InigoQuilez
+// https://iquilezles.org
+
 float dot2(vec2 v) { return dot(v, v); }
 float sdHeart(in vec2 p) {
   p.x = abs(p.x);