uniform vec2 resolution;

uniform float time;

#define rot(a) mat2(cos(a),sin(a),-sin(a),cos(a))

#define TAU atan(1.)*8.

#define changeSpeed 1.0

#define PI 3.1416

float cube(vec3 p,float r){vec3 q=abs(p)-r;return length(max(q,0.))+min(max(q.x,max(q.y,q.z)),0.);}

float octa(vec3 p,float r){return dot(abs(p),normalize(vec3(r)))-r;}

float map(vec3 p)

{

    p.xy*=rot(3.*PI/4.+time*.25);

    p.yz*=rot(PI/2.-time*.25);

    p.xz*=rot(PI/4.);

    float obj1 = cube(p, 5.15);

    float obj2 = octa(p, 4.);

    return  mix(obj1, obj2, (cos(time*changeSpeed)+1.)/2.);

}

void main(){

    vec4 display = vec4(0.0);

    vec2 uv=(gl_FragCoord.xy-.5*resolution)/resolution.y;

    vec3 rd=normalize(vec3(uv,1));

    vec3 p=vec3(0,0,-20);

    float d=1.,ix;

    for(int i=0;i<99;i++){

      p+=rd*(d=map(p));

      ix++;

      if (d<.001){break;}

    }

    if(d<.001) {

      display += 2./ix;

      display += mix(vec4(0.1,0.6,0.9,0),vec4(0.12,0.11,0.13,0),(cos(time*changeSpeed)+1.)/2.)*16./ix;

    }

    display.w=1.;

    gl_FragColor = display;

}