fix texture color issue on macos

shaders/circle.frag.hlsl

@@ -5,6 +5,9 @@
 float4 main(PSInput input) : SV_TARGET
 {
   float4 color = input.color;
-  color.a = abs(sdf.circle(input.uv, 1)) <= 0.05 ? 1:0 ;
+  float2 p = input.uv;
+  p -= 0.5;
+  p *= 2;
+  color.a = abs(sdf.circle(p, 1)) <= 0.005 ? 1:0 ;
   return color;
 }