Bouncy ball implemented in Java Processing

bounce.pde

float x;
float y;
float vx;
float vy;
int radius;
float ay;

void setup() {
  size(1000, 800);
  x = 500;
  y = 10;
  radius = 35;
  vx = 0;
  vy = 0;
  ay = 0.1;
}

void draw() {
  background(255, 255, 255);
  circle(x, y, radius);
  x = x + vx;
  y = y + vy;
  vy = vy + ay;
  if (y + radius > 800 && vy > 0) {
    vy = -vy * 0.9;
  };
}