// Author @patriciogv - 2015
// http://patriciogonzalezvivo.com

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 uResolution;
uniform float uTime;

float random (in vec2 _st) {
    return fract(sin(dot(_st.xy,
                         vec2(12.9898,78.233)))*
        43758.5453123);
}

// Based on Morgan McGuire @morgan3d
// https://www.shadertoy.com/view/4dS3Wd
float noise (in vec2 _st) {
    vec2 i = floor(_st);
    vec2 f = fract(_st);

    // Four corners in 2D of a tile
    float a = random(i);
    float b = random(i + vec2(1.0, 0.0));
    float c = random(i + vec2(0.0, 1.0));
    float d = random(i + vec2(1.0, 1.0));

    vec2 u = f * f * (3.0 - 2.0 * f);

    return mix(a, b, u.x) +
            (c - a)* u.y * (1.0 - u.x) +
            (d - b) * u.x * u.y;
}

#define NUM_OCTAVES 100
// Brightness (0.0 - 1.0)
#define BRIGHTNESS 0.55
#define LACUNARITY 2.0
#define GAIN 0.5
#define SHIFT 100.0

// VAR_THETA defines whether to compute
// sin/cos values at runtime or 
#define VAR_THETA 0
#define THETA 0.5
#if (VAR_THETA == 1)
#endif

float fbm ( in vec2 _st) {
    float v = 0.0;
    float a = BRIGHTNESS;
    // Rotate to reduce axial bias
    mat2 T = LACUNARITY * mat2(cos(THETA), sin(THETA), 
                               -sin(THETA), cos(THETA));
    for (int i = 0; i < NUM_OCTAVES; ++i) {
        _st = T * _st + SHIFT;
        v += noise(_st) * a;
        a *= GAIN;
    }
    return v;
}

#define SCALE 3.

void main() {
    vec2 st = gl_FragCoord.xy/uResolution.xy*SCALE;
    // st += st * abs(sin(uTime*0.1)*3.0);

    vec2 q = vec2(
        fbm( st + 0.*uTime),
    	fbm( st + vec2(1.0))
    );

    vec2 r = vec2(
    	fbm( st + 1.0*q + vec2(1.7,9.2)+ 0.15*uTime ),
    	fbm( st + 1.0*q + vec2(8.3,2.8)+ 0.126*uTime)
    );

    float f = fbm(st+r);

    vec3 color = mix(vec3(0.101961,0.619608,0.666667),
                vec3(0.666667,0.666667,0.498039),
                clamp((f*f)*4.0,0.0,1.0));

    color = mix(color,
                vec3(0,0,0.164706),
                clamp(length(q),0.0,1.0));

    color = mix(color,
                vec3(0.666667,1,1),
                clamp(length(r.x),0.0,1.0));

    gl_FragColor = vec4((f*f*f+.6*f*f+.5*f)*color,1.);
}