function setup() {
 createCanvas( 400, 400);
 background( 255 );
 stroke( 0 );
 strokeWeight( 2 );
 noFill();
 smooth();
 drawRects();
 }

 function draw() {
 }

 function drawRects() {
 background(255);
 for( var i = 0; i < 400; i++ ) {
 roundedRect( random(-10,width), random(-10,height), random( 5, 40), random(5,40), 5, 5 );
 }
 }

 function mousePressed() {
 drawRects();
 }

 function roundedRect(x, y, w, h, rx, ry) { 
 beginShape();
 vertex(x, y+ry); //top of left side
 bezierVertex(x, y, x, y, x+rx, y); //top left corner
 vertex(x+w-rx, y); //right of top side
 bezierVertex(x+w, y, x+w, y, x+w, y+ry); //top right corner
 vertex(x+w, y+h-ry); //bottom of right side
 bezierVertex(x+w, y+h, x+w, y+h, x+w-rx, y+h); //bottom right corner
 vertex(x+rx, y+h); //left of bottom side
 bezierVertex(x, y+h, x, y+h, x, y+h-ry); //bottom left corner
 endShape(CLOSE);
 }