SOURCE

let x=55;
let y=70;
let A=5
let B=7;
let d=50;
function setup(){
    createCanvas(600,600);
    noStroke();
    colorMode(HSB,328,30,96);
}
function draw(){
    //background(120,10);
    fill(random(295),23,91);
    x+=A;
    y+=B;
    if((x>500-d/2)||(x<d/2)){
        A=-A+random(-1,1);
    }
    if((y>500-d/2)||(y<d/2)){
        B=-B+random(-1,1);
    }
    triangle(x,y,x+60,y+70,x+130,y+50);
}

<script src='https://cdn.jsdelivr.net/npm/p5@1.1.9/lib/p5.min.js'></script><script src='https://cdn.jsdelivr.net/npm/p5@1.1.9/lib/p5.min.js'></script>