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float x,y,z;
void setup(){
size(800,500);
fill(0);
stroke(255);
}
void draw(){
background(0);
z+=.2;
for(x=0;x<2*PI;x+=PI/2){
for(y=0;y<1000;y+=5){
line(
y*cos(x),400-15*atan(cos(y/15+z)), x, y);
}
}
}