code: function(point, angle) {
      var x = point[0];
      var y = point[1];
      var si_z = Math.sin(angle);
      var co_z = Math.cos(angle);
      var newX = x * co_z - y * si_z;
      var newY = x * si_z + y * co_z;
      return [newX, newY];
    }
docs: Rotates the given point around the angle. @method _rotate @param point {Array} A point vector 2d. @param angle {Number} Angle for rotation [rad]. @return The rotated vector 2d.