This sketch is created with an older version of Processing,
and doesn't work on browsers anymore.
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size (800,800);
background (0);
for (int a= 3; a<700; a+=40){
for (int b=3; b<800; b+=50){
for (int c=6; c<800; c+=60){
stroke (1);
noFill();
stroke (random (150), random (255), random (0), 50);
beginShape();
curveVertex (b,b);
curveVertex (c,c);
curveVertex (c,b);
curveVertex (b,a);
endShape();
}}
}