// title: sketch-2020-01-08-00-24
// author: yue

#ifdef GL_ES
precision mediump float;
#endif

#define S3 1.73205080757
uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

void t(float r,vec2 center,inout vec3 color,vec2 point,float index){
    
    float dx=abs(center.x-point.x);
    float ybottom=1.-.5*r-center.y;
    float ytop=ybottom+(S3*r/3.-dx)*S3;
    if(dx<S3/2.*r&&point.y>ybottom&&point.y<ytop){
        color+=.4*vec3(point,sin(dx+index));
    }
}

void main(){
    const float r=.15;
    
    vec2 point=gl_FragCoord.xy/u_resolution;
    
    vec3 color=vec3(0.);
    for(float y=0.;y<=6.;y+=1.){
        vec2 tp=vec2(.5)+vec2(cos(u_time+y)*r,sin(u_time+y*y)*r);
        t(.1+.4*abs(sin(u_time+y)),tp,color,point,y);
    }
    
    gl_FragColor=vec4(color,1.);
}