* The robot is top-heavy, like most bipedal models today, yet still manages to balance.
* Narrow surfaces are more challenging than wide ones.
* Uneven or wobbly surfaces are more challenging than stable ones.
* The robot crosses its feet over each other. Look at the motion closely. The hip, knee, and ankle joints must be very sophisticated to support this level of agility.
Notice that this biped is still tethered. Here is an early video of the MIT robot cheetah, first in harness and then running free. (Warning: robot abuse ahead.) A more advanced version can climb over debris and recover from shoves. The current version can right itself after falls and even backflip. Compare this progression to the bipedal robot shown above and you can imagine where it might go in a few years.
I fucking love science. :D