// Example 07-22 from "Getting Started with Processing" 
// by Reas & Fry. O'Reilly / Make 2010

float angle = 0.0;

void setup() {
  size(120, 120);
  smooth();
}

void draw() {
  translate(mouseX, mouseY);
  float scalar = sin(angle) + 2;
  scale(scalar);
  strokeWeight(1.0 / scalar);
  rect(-15, -15, 30, 30);
  angle += 0.1;
}