Really cool! But it doesn't seem to be deterministic. I played a "perfect move", took it back, played it again, and it was downgraded to something less than perfect. Also, I took a different move back and was presented different pieces to move. Maybe the engine, given a chance to run longer, updates the list of best moves?
That's interesting, probably a bug in the take back function. There are multiple engine evaluations running in the background at the same time, current evaluation, opponent evaluation and the brain evaluation, so it could be possible that when you take back there is some problem with synchronization
