const g = 1; // Gravity

const jump = 20; // Jump power

const ground = 20;

const size = 20;

​

let x, y, vy;

​

function setup() {

  createCanvas(400, 400);

  x = width / 2;

  y = height - ground - size / 2;

  vy = 0;

}

​

function draw() {

  background(220);

  let gy = height - ground;

  line(0, gy, width, gy);

  ellipse(x, y, size, size);

  y += vy;

​

  if(y < height - ground - size / 2){ // in the air

    vy += g;

  }

  else{

    vy = 0;

    y = height - ground - size / 2;

  }

}

​

function mousePressed(){

  if(y >= height - ground - size / 2){ // on the ground

    vy = -jump;     

  }

}