One-Motor, All-Mechanical Obstacle Avoidance

OK, obstacle reflectance might be a better term, since this Lego Automatic Synchro Drive from YouTuber xyzzzach bounces off of obstacles, rather than actually avoiding them. But its design is so clever it deserves a bit of nomenclatural slack, IMHO. The entire ‘bot is surrounded by a spinning planetary-geared bumper. When the bumper contacts an object, it sticks, and its rotational momentum is transferred to a geared steering train that simultaneously rotates all four wheels, all of which are driven, away from the obstacle. And it’s all done with a single electric motor. Nice factory-style Lego assembly instructions here.