let x, y;

let dx = 0, dy = 0;

let speed = 0.5;

let resistance = 0.1;

​

function setup() {

  createCanvas(600, 600);

  x = width / 2;

  y = height / 2;

}

​

function draw() {

  background(220);

​

  fill(255, 0, 0);

  ellipseMode(CENTER);

  ellipse(x, y, size, size);

​

  checkKeyDown();

  moveEllipse();

}

​

function moveEllipse() {

  dx = constrain(dx, -5, 5);

  dy = constrain(dy, -5, 5);

  x = constrain(x + dx, size / 2, width - (size / 2));

  y = constrain(y + dy, size / 2, height - (size / 2));

  if(dx > 0) {

    dx -= resistance;

  }else if(dx < 0){

    dx += resistance;

  }

  if(dy > 0) {

    dy -= resistance;

  }else if(dy < 0){

    dy += resistance;

  }

}

​

function checkKeyDown() {

  if (keyIsDown(UP_ARROW)) {

    dy -= speed;

  }

  if (keyIsDown(RIGHT_ARROW)) {

    dx += speed;

  }

  if (keyIsDown(DOWN_ARROW)) {

    dy += speed;

  }

  if (keyIsDown(LEFT_ARROW)) {

    dx -= speed;

  }

}