def move_carrying(arg, speed, obstacles, obst_obstacles, obst_ramps)
      if speed
        x_d = arg.x - @x; y_d = arg.y - @y
        distance = Math.sqrt(x_d**2 + y_d**2)

        if distance == 0
          @speed.x = @speed.y = 0
          return
        end

        @speed.x = 1.0 * x_d * speed / distance
        @speed.y = 1.0 * y_d * speed / distance
      else
        arg += G.gravity
        @speed.x += arg.x / @mass; @speed.y += arg.y / @mass
        @speed.x = 0 if @speed.x.abs < G.min_speed.x
        @speed.y = 0 if @speed.y.abs < G.min_speed.y
        @speed.x = (@speed.x <=> 0) * @max_speed.x if @speed.x.abs > @max_speed.x
        @speed.y = (@speed.y <=> 0) * @max_speed.y if @speed.y.abs > @max_speed.y
      end

      x_aim = @x + @speed.x; y_aim = @y + @speed.y
      passengers = []
      obstacles.each do |o|
        if @x + @w > o.x && o.x + o.w > @x
          foot = o.y + o.h
          if foot.round(6) == @y.round(6) || @speed.y < 0 && foot < @y && foot > y_aim
            passengers << o
          end
        end
      end

      prev_x = @x; prev_y = @y
      if speed
        if @speed.x > 0 && x_aim >= arg.x || @speed.x < 0 && x_aim <= arg.x
          @x = arg.x; @speed.x = 0
        else
          @x = x_aim
        end
        if @speed.y > 0 && y_aim >= arg.y || @speed.y < 0 && y_aim <= arg.y
          @y = arg.y; @speed.y = 0
        else
          @y = y_aim
        end
      else
        @x = x_aim; @y = y_aim
      end

      forces = Vector.new @x - prev_x, @y - prev_y
      prev_g = G.gravity.clone
      G.gravity.x = G.gravity.y = 0
      passengers.each do |p|
        prev_speed = p.speed.clone
        prev_forces = p.stored_forces.clone
        prev_bottom = p.bottom
        p.speed.x = p.speed.y = 0
        p.stored_forces.x = p.stored_forces.y = 0
        p.instance_exec { @bottom = nil }
        p.move forces * p.mass, obst_obstacles, obst_ramps
        p.speed.x = prev_speed.x
        p.speed.y = prev_speed.y
        p.stored_forces.x = prev_forces.x
        p.stored_forces.y = prev_forces.y
        p.instance_exec(prev_bottom) { |b| @bottom = b }
      end
      G.gravity = prev_g
    end
def move_carrying(arg, speed, obstacles, obst_obstacles, obst_ramps)
      if speed
        x_d = arg.x - @x; y_d = arg.y - @y
        distance = Math.sqrt(x_d**2 + y_d**2)

        if distance == 0
          @speed.x = @speed.y = 0
          return
        end

        @speed.x = 1.0 * x_d * speed / distance
        @speed.y = 1.0 * y_d * speed / distance
      else
        arg += G.gravity
        @speed.x += arg.x / @mass; @speed.y += arg.y / @mass
        @speed.x = 0 if @speed.x.abs < G.min_speed.x
        @speed.y = 0 if @speed.y.abs < G.min_speed.y
        @speed.x = (@speed.x <=> 0) * @max_speed.x if @speed.x.abs > @max_speed.x
        @speed.y = (@speed.y <=> 0) * @max_speed.y if @speed.y.abs > @max_speed.y
      end

      x_aim = @x + @speed.x; y_aim = @y + @speed.y
      passengers = []
      obstacles.each do |o|
        if @x + @w > o.x && o.x + o.w > @x
          foot = o.y + o.h
          if foot.round(6) == @y.round(6) || @speed.y < 0 && foot < @y && foot > y_aim
            passengers << o
          end
        end
      end

      prev_x = @x; prev_y = @y
      if speed
        if @speed.x > 0 && x_aim >= arg.x || @speed.x < 0 && x_aim <= arg.x
          @x = arg.x; @speed.x = 0
        else
          @x = x_aim
        end
        if @speed.y > 0 && y_aim >= arg.y || @speed.y < 0 && y_aim <= arg.y
          @y = arg.y; @speed.y = 0
        else
          @y = y_aim
        end
      else
        @x = x_aim; @y = y_aim
      end

      forces = Vector.new @x - prev_x, @y - prev_y
      prev_g = G.gravity.clone
      G.gravity.x = G.gravity.y = 0
      passengers.each do |p|
        prev_speed = p.speed.clone
        prev_forces = p.stored_forces.clone
        prev_bottom = p.bottom
        p.speed.x = p.speed.y = 0
        p.stored_forces.x = p.stored_forces.y = 0
        p.instance_exec { @bottom = nil }
        p.move forces * p.mass, obst_obstacles, obst_ramps
        p.speed.x = prev_speed.x
        p.speed.y = prev_speed.y
        p.stored_forces.x = prev_forces.x
        p.stored_forces.y = prev_forces.y
        p.instance_exec(prev_bottom) { |b| @bottom = b }
      end
      G.gravity = prev_g
    end
Moves this object as an elevator (i.e., potentially carrying other
 objects) with the specified forces or towards a given point.

 Parameters:
 [arg] A Vector specifying either the forces acting on this object or a
       point towards the object should move.
 [speed] If the first argument is a forces vector, then this should be
         +nil+. If it is a point, then this is the constant speed at which
         the object will move (provided as a scalar, not a vector).
 [obstacles] An array of obstacles to be considered in the collision
             checking, and carried along when colliding from above.
             Obstacles must be instances of Block (or derived classes),
             or objects that <code>include Movement</code>.
 [obst_obstacles] Obstacles that should be considered when moving objects
                  from the +obstacles+ array, i.e., these obstacles won't
                  interfere in the elevator's movement, but in the movement
                  of the objects being carried.
 [obst_ramps] Ramps to consider when moving objects from the +obstacles+
              array, as described for +obst_obstacles+.