code: function(v) {
          if(v instanceof Vec3){
              return this.toVec3()._cross(v);
          }
          return new Vec3(0,0, this.x * v.y - this.y * v.x);
      }
docs: Computes the cross product with a Vec2 or Vec3. Note that by definition the cross product of two 2D vectors is a 3D vector with x = y = 0
  @memberof Vec2#
  @param   {Vec2|Vec3} v
  @returns {Vec3}