This 2D side-view simulator lets you build a block-and-tackle out of fixed and movable pulleys and see mechanical advantage in action: choose a configuration from a single fixed pulley up to a four-part double-block tackle, set the load's mass and the effort force you pull the rope with, and watch the load rise or sink according to real physics — mechanical advantage equals the number of rope segments carrying the load, the effort force needed is the load's weight divided by that number, and the rope always travels exactly that many times farther and faster than the load itself.