brigid_fitch: Holy cats, there's an entire video of these kinds of robots!

Yup. People have been doing that for decades now. IIRC it first started in Denver, Colorado of all places.
The heavier weight classes can be pretty straightforward and have room for kinetic weapons, but the lighter ones are very challenging to design.
Making a robot in the smallest (sub 1 kilogram) classes can be very challenging to do as there just isn't much overhead for simply attaching hammers or spikes, you have to get everything in a small package and come up with something really innovative as to how it attacks and defends.

brigid_fitch: Dryad: brigid_fitch: Holy cats, there's an entire video of these kinds of robots!

Yup. People have been doing that for decades now. IIRC it first started in Denver, Colorado of all places.
The heavier weight classes can be pretty straightforward and have room for kinetic weapons, but the lighter ones are very challenging to design.
Making a robot in the smallest (sub 1 kilogram) classes can be very challenging to do as there just isn't much overhead for simply attaching hammers or spikes, you have to get everything in a small package and come up with something really innovative as to how it attacks and defends.

I'm a HUGE fan of Battlebots--have been since their original run on Comedy Central.  Just never seen bots this QUICK before and able to stop on a dime like that!

I loved Battlebots as well, that was straight up violently smashing stuff which was cool as hell. A lot of the smaller competitions allowed for or even required a lot subtler range of tactics and styles though. Even robots that split into multiple separate units. Being sneaky or agile or tricky is as much a part of it, more likely to have someone throw a net or try to jam your tracks for an immobilization win than try to smash you outright. Looks like this Japanese video is very much a non-destructive sumo style match.
When Battlebots first launched, they reached out to the folks already doing this kind of thing and came to existing competitions hoping to get their first batch of competitors. I was excited and REALLY wanted to be part of it at first, just like most Critter Crunch folks, but as I dove into the contracts I noticed they severely limited the allowable designs in a way it was clear they very much wanted a robot MMA.
Super fun and awesome in its own right, but it was just so far from the type of designs most of us fielded at the time. It was like walking into a fencing competition and asking for heavyweight boxers.