[casercaramel144]

I was curious as to how it works, so I implemented here: turingmachine.io/?import-gist=c862f28918f3d889f964797694d28fcc

If you run it for a bit you see what's going on, State B turns 0's into 2's and 1's into 1's transitioning to C and state C turns 3 -> 2's and transitions to A. So you just iteratively lengthen your run of 3's exponentially since it requires a full pass through all the 3's to fix a 2->1.

[tux3]

It's fairly easy to make a turing machine that goes exponential and blows up forever.

But the really tricky part to understand is why it eventually stops. After an unimaginably high number of steps.