// Author @patriciogv ( patriciogonzalezvivo.com ) - 2015
// Title: Diamond Tiles

#ifdef GL_ES
precision mediump float;
#endif

// Copyright (c) Patricio Gonzalez Vivo, 2015 - http://patriciogonzalezvivo.com/
// I am the sole copyright owner of this Work.
//
// You cannot host, display, distribute or share this Work in any form,
// including physical and digital. You cannot use this Work in any
// commercial or non-commercial product, website or project. You cannot
// sell this Work and you cannot mint an NFTs of it.
// I share this Work for educational purposes, and you can link to it,
// through an URL, proper attribution and unmodified screenshot, as part
// of your educational material. If these conditions are too restrictive
// please contact me and we'll definitely work it out.

#define PI 3.14159265358979323846

uniform vec2 u_resolution;
uniform float u_time;

vec2 rotate2D(vec2 _st, float _angle){
    _st -= 0.5;
    _st =  mat2(cos(_angle),-sin(_angle),
      sin(_angle),cos(_angle)) * _st;
    _st += 0.5;
    return _st;
}

vec2 tile(vec2 _st, float _zoom){
    _st *= _zoom;
    return fract(_st);
}

float box(vec2 _st, vec2 _size, float _smoothEdges){
    _size = vec2(0.5)-_size*0.5;
    vec2 aa = vec2(_smoothEdges*0.5);
    vec2 uv = smoothstep(_size,_size+aa,_st);
    uv *= smoothstep(_size,_size+aa,vec2(1.0)-_st);
    return uv.x*uv.y;
}

vec2 offset(vec2 _st, vec2 _offset){
    vec2 uv;

    if(_st.x>0.5){
        uv.x = _st.x - 0.5;
    } else {
        uv.x = _st.x + 0.5;
    }

    if(_st.y>0.5){
        uv.y = _st.y - 0.5;
    } else {
        uv.y = _st.y + 0.5;
    }

    return uv;
}

void main(void){
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    st.y *= u_resolution.y/u_resolution.x;

    st = tile(st,10.);

    vec2 offsetSt = offset(st,vec2(0.5));

    st = rotate2D(st,PI*0.25);

    vec3 color = vec3( box(offsetSt,vec2(0.95),0.01) - box(st,vec2(0.3),0.01) + 2.*box(st,vec2(0.2),0.01) );

    gl_FragColor = vec4(color,1.0);
}