Algodoo

The gearbox of the (at least some/current-model) Prius. In the real car, the inner and outer gears are driven by electric motors and the middle ring by the gas engine. See here:
http://eahart.com/prius/psd/
for more—hard to explain.

That animation is much better for understanding how it works, but I thought I'd recreate it in Phun.

Also, first scene!

EDIT: Forgot to include controls:

Left/Right/Down—control outer gear. (Fwd/Rev/Brake)
A/D/S—control inner gear
Shift/Ctrl—control ring (Fwd/Brake only, as it would be in real life).

Also, the ring is only a gear because that was easier than using CSG to make a non-toothed ring.