#version 150
// uniforms
uniform sampler2D texture_sampler;
// input
varying vec2 frag_uv;

void main() {
  float t = texture2D(texture_sampler, frag_uv + vec2( 0.0f, -0.01f )).a;
  float b = texture2D(texture_sampler, frag_uv + vec2( 0.0f, 0.01f )).a;
  float c = 0.0f;
  if (t < 0.75 && b > 0.75) {
	c += 0.5f;
  }
  gl_FragColor = vec4(0.75, 0.5, 0.5, c);
  if (gl_FragColor.a == 0.0) discard;
  //gl_FragColor = vec4(0.5, 0.0, 0.0, 0.5);
}