processing4/java/examples/Books/Nature of Code/introduction/RandomWalkPVector/Walker.pde

// Random Walker (No Vectors)
// Daniel Shiffman <http://www.shiffman.net>
// The Nature of Code
// A random walker class!

class Walker {
  PVector loc;

  Walker() {
    loc = new PVector(width/2,height/2);
  }

  void render() {
    stroke(0);
    fill(175);
    rectMode(CENTER);
    rect(loc.x,loc.y,40,40);
  }

  // Randomly move up, down, left, right, or stay in one place
  void walk() {
    PVector vel = new PVector(random(-2,2),random(-2,2));
    loc.add(vel);
    
    // Stay on the screen
    loc.x = constrain(loc.x,0,width-1);
    loc.y = constrain(loc.y,0,height-1);
  }
}