HopTo’s Hop-1 is a hybrid hopping-and-flying robot built for rough terrain. It looks weird at first, but the logic is actually pretty smart. Flying all the time burns a ton of energy just fighting gravity, so they let the robot spend most of its time bouncing on a passive spring instead. The rotors mainly steer, put back the energy lost on each hop, and only fully take over when the robot actually needs to fly. HopTo says hopping uses around 25% of the energy of continuous flight. So the whole idea is pretty simple: stay on the ground as much as possible, and only fly when you have to.