#version 330 core
out vec4 FragColor;
in vec2 vUV;
uniform vec2 iResolution;
uniform float iTime;

vec3 palette( float t) {
    vec3 a = vec3(1.0, 0.5, 0.5);
    vec3 b = vec3(1.0, 0.5, 0.5);
    vec3 c = vec3(1.0, 1.0, 1.0);
    vec3 d = vec3(0.263, 0.416, 0.557);
    return a + b * cos( 6.28318 * (c * t * d) );
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec2 uv = (fragCoord * 2.0 - iResolution.xy) / iResolution.y;
    float d = length(uv);
    vec3 col = palette(d);
    d = sin(d * 8.0 + iTime) / 8.0;
    d = abs(d);
    d = 0.02 / d;
    col *= d;
    fragColor = vec4(col, 1.0);
}

void main() {
    vec2 fragCoordPixels = vUV * iResolution;
    vec4 outColor;
    mainImage(outColor, fragCoordPixels);
    FragColor = outColor;
}