​

function rot(theta,v) {

  return [(v.x*cos(theta))-(v.y*sin(theta)),(v.x*sin(theta))+(v.y*cos(theta))]

}

function setup() {

  createCanvas(400, 400);

  v=createVector(0,0);

}

function draw() {

  v.y=keyIsDown(87);//w

  v.y-=keyIsDown(83);//s

  v.x=-keyIsDown(65);//a

  v.x+=keyIsDown(68);//d

  background(220);

  v.normalize();

  // if (v.y<1) {v.x*=-1}

  text("x:"+v.x+", y:"+v.y,10,height/2);

  [v.x,v.y]=rot(-PI/4,v);

  text("left:"+v.x,10,height/2+10);

  text("right:"+v.y,10,height/2+20);

}