A double pendulum is a pendulum with another pendulum attached to its end, and is a simple physical system[?] that exhibits rich dynamic behavior[?]. The double pendulum is governed by very complicated formulas that can be found here (http://scienceworld.wolfram.com/physics/DoublePendulum). The double pendulum relates to:
... player controls the direction and speed of movement (it's a 3-speed stick). Gameplay is very challenging and rewarding, and once the player has gotten through a level there ...