class Ball {
  float x, y;          // position
  float vx=0, vy=0;    // velocity in the two directions   
  float r=2.5;         // radius
  float gravity=0.05;  // the amount of acceleration
  color c;
  
  // Initialize a Ball at position (x0,y0)
  Ball(float x0, float y0, color c)
  {
    x = x0; 
    y = y0;
    this.c = c;
  }

  void draw()
  {
    fill(c);
    ellipse(x,y,r*2,r*2);
  }

  void update()
  {
    // Accelerate according to gravity
    vy += gravity;
    // Move in the appropriate direction by the step size
    x += vx;
    y += vy;
  
    // Bounce   
    if (y > height-r) {
      y = height-r;
      vy = -vy;
    }
  }
}