let circlePosY;

let speedX = 5;

let speedY = 7;

let circleRadius;

​

function setup() {

  createCanvas(640, 640);

  circleRadius = width / 16;

  circlePosX = circleRadius;

  circlePosY = circleRadius;

  noStroke();

}

​

function draw() {

  // EASY TRAILS

  // instead of background

  // draw a full screen rect (with no stroke)

  // the color you want your background

  // with some alpha value

  fill(255, 25);

  rect(0, 0, width, height);

​

  fill(255, 120, 0, 200);

  circle(circlePosX, circlePosY, circleRadius * 2);

​

  circlePosX += speedX;

  circlePosY += speedY;

​

  // bounce the ball off walls with if statements with OR, which is two pipes: ||

  if (circlePosX > width - circleRadius || circlePosX < circleRadius) {

    speedX *= -1;

  }

​

  if (circlePosY > height - circleRadius || circlePosY < circleRadius) {

    speedY *= -1;

  }

}

​