#version 100
precision mediump float;
uniform float u_time;
uniform vec2 u_resolution;

void main() {
    vec2 uv = (gl_FragCoord.xy * 2.0 - u_resolution.xy) / u_resolution.y;
    
    // Auto zoom
    float zoom = 1.0 + sin(u_time * 0.1) * 0.5;
    zoom = pow(zoom, 4.0);
    vec2 c = uv / zoom - vec2(0.74364388703, 0.13182590421); // Zoom into a specific interesting point
    
    vec2 z = vec2(0.0);
    float iter = 0.0;
    float max_iter = 100.0;
    
    for (float i = 0.0; i < 100.0; i++) {
        z = vec2(z.x * z.x - z.y * z.y, 2.0 * z.x * z.y) + c;
        if (length(z) > 4.0) break;
        iter += 1.0;
    }
    
    float f = iter / max_iter;
    vec3 col = vec3(f);
    col = 0.5 + 0.5 * cos(3.0 + f * 10.0 + vec3(0.0, 0.6, 1.0));
    
    if (iter >= 99.0) col = vec3(0.0);
    
    gl_FragColor = vec4(col, 1.0);
}