//philip.bertani@gmail.com
//kifs dist func taken from Shane's - https://www.shadertoy.com/view/XsKXzc - and modified
//Code was graciously golfed and refactored by FabriceNeyret2 (see https://www.shadertoy.com/view/7tcBDn)

#define R(a)  mat2(cos(a + 1.57*vec4(0,-1,1,0)))  //rotation matrix using pi/2 phase offset for sin
#define N     normalize

float t, e=1., l=0., d, i=0.; // globals
vec2 mm;  //Mouse

float f(vec3 p) {
    vec3  o = vec3(1,.75,.15), q;
    float d=1e6, s=-.006, a=1.,r=.02, i=0., k = o.z*s;
    for( p.xz *= R(t/7.) ; i++<17. ; )
        a *= 1.-s,
        p.xy *= R(mm.x), p.yz *= R(mm.y), // rotations here have large impact on shape
        p = abs(p),
#define S(p) p.x < p.y ? p = p.yx : p     
        S(p.xy), S(p.xz), S(p.yz),  // sort
        p = mix( p, o, s),
        p.z < k*.5 ? p.z -= k : d,
        q = p = abs(p),
        S(q.xy), S(q.xz), S(q.yz),  // sort
        d = min(d, max( q.x/a - r, -q.y/a +r-.002 ) );
    return d;
}

void mainImage(out vec4 O, vec2 U) {
    t = iTime;
    vec3 R = iResolution, E = vec3(1,-1,-1), n,
         L =  vec3(sin(t*2.),0.,-1.),        // light pos
         D = N( vec3( U+U,-R.y) - R.xyy ),   // ray pos and dir
         P = R-R; P.z = max(0., .24 - max(.7*sin((t+6.28)/2.),0.));

    mm = 5.*(iMouse.xy-2.*R.xy)/R.y; if(iMouse.w==0.)mm=5.*vec2(.23,.09);
    
    for ( O-=O ; i++<1e2 && l<3. && e>0.; P += d*D ) {
        l += d = f(P)*.7;
        e = d - (1.+l*l)/4e4;
        if( e < 0. ) {
            P += e*D;
            L = N(L-P);
#define F(x)  x* f( P + (1.+l*l)/2e3 *x )
            n = N( F(E.x)+F(E.yyx)+F(E)+F(E.yxy) );  // normal vec
            O.rgb =  .3* max(0.,dot(-n,L)) *vec3(.7,.5,0.)
                    +.6* pow(max(0.,dot(reflect(-D,n),L)),4.) *vec3(.9,.8,.3);
            O = pow( 5.*(1.-exp(-O*O)) /exp(l*l*60.),vec4(.4) ); 
            break; 
          }
    }
}