#define DTR 0.0174532
#define rot(a) mat2(cos(a),sin(a),-sin(a),cos(a))

vec2 uv;
vec3 cp,cn,cr,ro,rd,ss,oc,cc,gl,vb;
vec4 fc;
float tt,cd,sd,io,oa,td;
int es=0,ec;
 
//shapes:
float bx(vec3 p,vec3 s){vec3 q=abs(p)-s;return min(max(q.x,max(q.y,q.z)),0.)+length(max(q,0.));}

//crystal - domain repetition with a rotated lattice
vec3 latticeA(vec3 p, int iter)
{
	for(int i = 0; i < iter; i++)
	{
        p.xy *= rot(45.*DTR);
		p.xz *= rot(45.*DTR);
		p=abs(p)-1.;
        
        //this reverse-rotation to bring the cubes back is actually "wrong",
        //swap these two lines for the "proper" symmetric lattice
		p.xy *= rot(-45.*DTR);
		p.xz *= rot(-45.*DTR);
	}
	return p;
}

//scene
float mp(vec3 p)
{
//now with mouse control
if(iMouse.z>0.){
    p.yz*=rot(2.0*(iMouse.y/iResolution.y-0.5));
    p.zx*=rot(-7.0*(iMouse.x/iResolution.x-0.5));
}
	vec3 pp = p;	
	p.xz*=rot(tt*0.2);
    p = latticeA(p, 5);
    sd=bx(p,vec3(1.)) - 0.03;
    float osc = cos(tt * 2.)*0.5+0.5;
	sd = mix(sd, length(pp) - 1., min(pow(sin(tt*0.5)*0.5+0.5, 3.) + osc*0.1,1.));	
	sd=abs(sd)-0.001;
	if(sd<0.001)
	{
		oc=vec3(1.,0,0.25);
		io=1.2;
		oa=0.8-length(pp*0.1);
		ss=vec3(0.);
		vb=vec3(0.,2.5,2.5);
		ec=2;	
	}
	return sd;
}

//raymarching and normals
void tr(){vb.x=0.;cd=0.;for(float i=0.;i<512.;i++){mp(ro+rd*cd);cd+=sd;td+=sd;if(sd<0.0001||cd>128.)break;}}
void nm(){mat3 k=mat3(cp,cp,cp)-mat3(.001);cn=normalize(mp(cp)-vec3(mp(k[0]),mp(k[1]),mp(k[2])));}

//pixel colouring
void px()
{
  cc=vec3(1.,0.45,0.)+length(pow(abs(rd+vec3(0,0.5,0)),vec3(3)))*0.3+gl;
  if(cd>128.){oa=1.;return;}
  vec3 l=vec3(0.4,0.7,0.8);
  float df=clamp(length(cn*l),0.,1.);
  vec3 fr=pow(1.-df,3.)*mix(cc,vec3(0.4),0.5);
  float sp=(1.-length(cross(cr,cn*l)))*0.2;
  float ao=min(mp(cp+cn*0.3)-0.3,0.3)*0.5;
  cc=mix((oc*(df+fr+ss)+fr+sp+ao+gl),oc,vb.x);
}

//basic setup and transparency loop
void mainImage(out vec4 fragColor, in vec2 fragCoord )
{
  tt=mod(iTime, 260.);
  uv=vec2(fragCoord.x/iResolution.x,fragCoord.y/iResolution.y);
  uv-=0.5;uv/=vec2(iResolution.y/iResolution.x,1);
  ro=vec3(0,0,-15);rd=normalize(vec3(uv,1));
  
  for(int i=0;i<20;i++)
  {
	tr();cp=ro+rd*cd;
    nm();ro=cp-cn*0.01;
    cr=refract(rd,cn,i%2==0?1./io:io);
    if(length(cr)==0.&&es<=0){cr=reflect(rd,cn);es=ec;}
    if(max(es,0)%3==0&&cd<128.)rd=cr;es--;
	if(vb.x>0.&&i%2==1)oa=pow(clamp(cd/vb.y,0.,1.),vb.z);
	px();fc=fc+vec4(cc*oa,oa)*(1.-fc.a);	
	if((fc.a>=1.||cd>128.))break;
  }
  
  fragColor = fc/fc.a;
}