#version 300 es
precision mediump float;

in vec2 texCoord;

uniform sampler2D selection;
uniform float spacing;
uniform float threshold;
uniform float time;
uniform vec4 borderColor1;
uniform vec4 borderColor2;
uniform float centerSampleMix;

out vec4 fragColor;

void main() {
	float centerSample = step(threshold, texelFetch(selection, ivec2(texCoord), 0).r);
	float luminance = step(0.5, mod(gl_FragCoord.x + gl_FragCoord.y + time * 2.0 * spacing, spacing) / spacing);
	fragColor = mix(borderColor1, borderColor2, luminance) * centerSample * centerSampleMix;
}