SOURCE

let x=50;
let d=50;
let y=50
let a=20
let b=30
function setup(){
    createCanvas(500,500);
    noStroke(0);
}
function draw(){
    background(120);
    x+=a;
    fill(random(1));
    if((x>550)||(x<0)){;a=-a
       ;
    }  
    y+=b;
    fill(random(255));
    if((y>550)||(y<0)){b=-b
       ;
    }
    ellipse(x,y,d,d);
}

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