Animation

Animation is just changing images really fast. To draw a circle at a different location for every frame you can use the following code:

let xPosition = 0;
let xVelocity = 1;

function setup(){
  size(400, 400);
}

function draw(){
    background(220);
    circle(xPosition, height/2, 100);
    xPosition += xVelocity; // move the circle to the right 
}

By changing the velocity in x and y direction you can make the circle move diagonally:

let xPosition;
let yPosition;
let xVelocity = 2;
let yVelocity = 3;

function setup(){
  size(800, 600);
  xPosition = width/2; 
  yPosition = height/2;
}

function draw(){
    circle(xPosition, yPosition, 20);
    xPosition += xVelocity;
    yPosition += yVelocity;

    // bounce
    if (xPosition > width || xPosition < 0) xVelocity = -xVelocity;
    if (yPosition > height || yPosition < 0) yVelocity = -yVelocity;
}


Bounce a ball across the canvas