Pulley simulator in 3D: a fixed pulley, a movable pulley and block and tackle systems, factorial and exponential, with 1 to 4 movable pulleys. Hang a load, lift it by pulling the rope and see how much force you need and how much rope you pull in: F = R/2n in the factorial system and F = R/2ⁿ in the exponential one, with the efficiency of each pulley. The rope and the pulleys follow the DIN 15020 standard, and the “Design your pulley system” mode finds how many pulleys you need for your maximum force.