// A quick example to show use of if-statements
// to keep a moving ball (also how to use delta variables)
// withing sketch bounds...

// The x, y, deltaX, deltaY for controlling the ball
// location and movement
int x;
int y;
int deltaX = 1;
int deltaY = 1;

// ball size
int ballSize = 25;

void setup() {
  size(400, 400);
  smooth();

  x = int(random(width));
  y = int(random(height));
} // setup()

void draw() {
  background(255);

  drawBall(x, y, ballSize);

  x = x + deltaX;
  y = y + deltaY;

  // did I reach the right or left edge of the sketch?
  if ((x > width) || (x < 0)) {
    
    // move backwards
    deltaX = -deltaX;
  }

  // top edge? or bottom edge?
  if ((y < 0) || (y > height)) {
    deltaY = -deltaY;
  }
} // draw()

void drawBall(int x, int y, int w) {
  noStroke();
  fill(#FA72DA);
  ellipse(x, y, w, w);
} // drawBall()