rotateAwayFrom(vec, center, angle) {
    this.rotateAround(angle, center);
    let distSqA = this.distanceSq(vec);
    this.rotateAround(-2.0 * angle, center);
    let distSqB = this.distanceSq(vec); // If it was rotated towards the other vertex, rotate in other direction by same amount.

    if (distSqB < distSqA) {
      this.rotateAround(2.0 * angle, center);
    }
  }
Rotates the vector away from a specified vector around a center.

@param {Vector2} vec The vector this one is rotated away from.
@param {Vector2} center The rotational center.
@param {Number} angle The angle by which to rotate.