Challenge2.pde

float y = 55.0;
float x = 55.0;
float stepY = 3.0;
float stepX = 3.0;
float radio = 55.0;

void setup() {
  size(500, 500);
  noStroke();
  ellipseMode(RADIUS);
}

void draw() {
  background(0);

  ellipse(x, y, radio, radio);

  // Update position
  x += stepX;
  y += stepY;

  // Bounce vertically
  if (y > height - radio || y < radio) {
    stepY = -stepY;
  }

  // Bounce horizontally
  if (x > width - radio || x < radio) {
    stepX = -stepX;
  }
}