let trianglePosY = 200;

let circlePosX;

let circlePosY;

let speedX = 5;

let speedY = 9;

let circleRadius;

​

function setup() {

  createCanvas(600, 400);

  circleRadius = width/50;

  circlePosX = circleRadius;

  circlePosY = circleRadius;

}

​

function draw() {

  // background(255);

  // keeps redrawing background till transparency adds up

  fill(255,10)

  rect(0,0,width,height)

​

  noStroke();

  fill(255, 120, 0, 200);

  circle(circlePosX, circlePosY, circleRadius * 2);

​

  circlePosX += speedX;

  circlePosY += speedY;

​

​

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

    speedX *= -1;

  }

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

    speedY *= -1;

  }

}

​