// http://forum.processing.org/topic/not-running-in-browser-or-javascript-mode-why

final static int NUM = 8, DIM = 50;
final RectPush[] rects = new RectPush[NUM];

boolean up, down, right, left;

void setup() {
  size(600, 300);
  textAlign(CENTER);
  rectMode(CORNER);

  for (int i=0; i!=NUM; i++) {
    final int x = (int) random(width  - DIM);
    final int y = (int) random(height - DIM);
    rects[i] = new RectPush(x, y, DIM, i);
  }
}

void draw() {
  background(#00CAFF);
  noStroke();

  for (int i=0; i!=NUM; i++) {
    final RectPush r = rects[i];

    if (r.x < mouseX & mouseX < r.x + DIM & r.y < mouseY & mouseY < r.y + DIM) {
      fill(#FFC800);

      if (right)   ++rects[i].x;
      if (left)    --rects[i].x;
      if (down)    ++rects[i].y;
      if (up)      --rects[i].y;
    }

    else   fill(-1);

    rects[i].update();
  }
}

void keyPressed() {
  if (keyCode == UP)     up    = true;
  if (keyCode == DOWN)   down  = true;
  if (keyCode == LEFT)   left  = true;
  if (keyCode == RIGHT)  right = true;
}

void keyReleased() {
  up = down = right = left = false;
}

class RectPush {
  int x, y;
  int dim;
  int i;

  RectPush(int _x, int _y, int _dim, int _i) {
    x = _x;
    y = _y;
    i = _i;
    dim = _dim;
  }

  void update() {
    rect(x, y, dim, dim);
    fill(#FF0077);
    text(i, x+25, y+30);
  }
}