diff --git a/engine/app_shaders.cpp b/engine/app_shaders.cpp
index 2bce50b..d60799a 100644
--- a/engine/app_shaders.cpp
+++ b/engine/app_shaders.cpp
@@ -322,7 +322,17 @@ void App::initShaders()
 #else
         "out mediump vec4 frag;\n"
 #endif
-        "mediump float rand(mediump vec2 co) { return fract(sin(dot(co.xy, vec2(12.9898, 78.233))) * 43758.5453); }\n"
+        // http://byteblacksmith.com/improvements-to-the-canonical-one-liner-glsl-rand-for-opengl-es-2-0/
+        "highp float rand(mediump vec2 co)\n"
+        "{\n"
+        "    highp float a = 12.9898;\n"
+        "    highp float b = 78.233;\n"
+        "    highp float c = 43758.5453;\n"
+        "    highp float dt= dot(co.xy ,vec2(a,b));\n"
+        "    highp float sn= mod(dt,3.14);\n"
+        "    return fract(sin(sn) * c);\n"
+        "}\n"
+        //"highp float rand(mediump vec2 co) { return fract(sin(dot(co.xy, vec2(12.9898, 78.233))) * 43758.5453); }\n"
         "void main(){\n"
         "   mediump vec2 uv2 = gl_FragCoord.st / resolution;\n"
         "   mediump float stencil = 1.0 - (texture(tex_stencil, (uv2+stencil_offset) * 2.0).r * 0.9) * stencil_alpha;\n"