[chbot] A human-like walking robot that requires no power source...

[hamster]

... as long as it is down hill.

"Last year, BlueBiped successfully walked for 13 hours continuously —
100,000 consecutive steps, 9 miles (15km) — without human intervention"

So simple that it boggles my mind - it looks so obvious!

Video is on
http://www.extremetech.com/extreme/101525-bluebiped-a-human-like-walking-robot-that-requires-no-power-source