#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform float u_time;
uniform vec2 u_mouse;

float random(in float x) {
    return fract(sin(x)*1e6);
}

float randcol(float x, float f, float t) {
    return step(0.75,random(floor(x*f)-floor(t)));
}

void main() {
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    st.x *= u_resolution.x/u_resolution.y;

    float cols = 64.;
    float freq = random(floor(u_time))+abs(atan(u_time)*.1);
    float t = 40.*u_time*(1.-freq);

    if (gl_FragCoord.y < u_mouse.y && st.y < 0.9) {
        gl_FragColor = vec4(1.);
        return;
    }

    if (fract(st.y*cols*.5) < .5) t *= -1.;

    freq += random(floor(st.y*20.));

    float offset = .025;
    vec3 color = vec3(randcol(st.x, freq*100.+random(freq), t+offset),
                      randcol(st.x, freq*100., t),
                      randcol(st.x, freq*100.+random(freq), t-offset));

    gl_FragColor = vec4(1.-color,1.);
}