Vector example from class.

solution.js

const vec2 = glMatrix.vec2;

window.init = (canvas) => {
  console.log('Init()!!!!!!!!!');

  // TODO
};


window.loop = (dt, canvas) => {
  const ctx = canvas.getContext('2d');

  const center = vec2.fromValues(
    canvas.width / 2,
    canvas.height / 2,
  );

  ctx.moveTo(center[0], center[1]);
  
  const direction = vec2.create();
  const rotated = vec2.create();
  const down = vec2.fromValues(0, -1);
  vec2.rotate(
    rotated,
    down,
    vec2.create(),
    Math.PI / 6);
  vec2.scale(direction, rotated, 100);
  ctx.lineTo(center[0] + direction[0], center[1] + direction[1]);

  ctx.stroke();
};