precision mediump float;

uniform vec2 iResolution; // viewport resolution (in pixels)
uniform float iTime; // shader playback time (in seconds)
uniform vec2 iMouse; // mouse pixel coords. xy: current (if MLB down), zw: click

vec3 palette(float t) {
    //https://iquilezles.org/articles/palettes/
    vec3 a = vec3(0.1, 0.1, 0.1);
    vec3 b = vec3(0.5, 0.5, 0.5);
    vec3 c = vec3(1.0, 1.0, 1.0);
    vec3 d = vec3(0.0, 0.33, 0.67);

    return a + b * cos(1.28318 * (c * t + d));