Interesting low-cost measure to not use a front-derailleur

The S2 model aimed to give riders an uphill climbing gear but without introducing the complexities of a gear-shifting derailleur, tensioned cables, and handlebar shifters. Engineers at SRAM came up with a solution that's hard to imagine for other bikes but not too hard to grasp. A freewheel in the back has two cogs, with a high gear for cruising and a low gear for climbing. If you pedal backward a half-rotation, the outer, higher gear engages or disengages, taking over the work from the lower gear. The cogs, chains, and chainrings on this bike are always moving, but only one gear is ever doing the work.

Probably not of much use but I thought it was cool