// Bouncing ball simulation

// Variables
int ballX = 200;
int ballY = 150;
int ballWidth = 30;
int moveAmount = 2;
int fallAmount = 1;
int windowWidth = 600;
int windowHeight = 400;

void setup()
{
  size(windowWidth, windowHeight);
  smooth(); // get rid of jagged edges
}

void draw ()
{
  // Draw ball at current position
  background(150);
  ellipse(ballX, ballY, ballWidth, ballWidth);
  
  // Move ball for next call to draw()
  ballX = ballX + moveAmount;
  ballY = ballY + fallAmount;
  
  // Make sure ball doesn't move offscreen
  int distanceToRightEdge = windowWidth - ballX;
  int distanceToLeftEdge = ballX;
  int distanceToSide = abs(distanceToRightEdge - distanceToLeftEdge);
  if (distanceToSide > (windowWidth - ballWidth) )
  {
    // Reverse direction
    moveAmount = -1 * moveAmount;
  }
  
  int distanceToBottom = windowHeight - ballY;
  int distanceToTop = ballY;
  int distanceToEdge = abs(distanceToBottom - distanceToTop);
  if (distanceToEdge > (windowHeight - ballWidth))
  {
    fallAmount = -1 * fallAmount;
    
    // Change ball color
    int redComponent = (int)random(256);
    int greenComponent = (int)random(256);
    int blueComponent = (int)random(256);
    fill(redComponent, greenComponent, blueComponent);
  }
}