By 2018, it was hopping continuously to heights up to a meter (3.3 ft) or so, with pretty decent accuracy, and autonomously bouncing its way up obstacles, using chairs as stepping stones to bounce up onto a table, for example.

What it couldn't do, oddly enough, was land. It's one thing to keep a jigger like this dynamically in motion, but things need to be incredibly precise to stick the landing, especially when you don't have a second leg to step forward or back if you land at the wrong angle.

Indeed, angular momentum is the biggest bugbear for Salto to deal with, particularly when hopping forward from one spot to another. It leans forward as it jumps, using a rotating reaction wheel to balance, then adjusts the rotation of that balance wheel to bring its foot forward to the appropriate angle for a controlled landing. If its angular momentum is off, it might land its foot right on the target but then fall over.

Salto team lead Justin Yim explained the solution in an interview with IEEE Spectrum. "Falling from 1 meter (3 ft), Salto only has about 2.3 degrees of wiggle room forwards and backwards if it is to stick its landing. Gymnasts 'sticking a landing' with feet together face this same challenge. If their angular momentum is wrong, they have to take a step to keep their balance. However, taking a step isn't possible with only one leg (as Salto has) or when landing on a narrow ledge or beam. A person landing on a beam or ledge will pinwheel their arms the same way Salto spins its reaction wheel tail."