In Mazerunner, your code is a maze which is traversed by a rat that always walks along the left wall. If you don't feed the rat enough cheese, it dies from starvation. If you feed it too quickly, it dies from overfeeding.
The rat starts at 'S', eats cheese at 'c' and finishes the program at 'C' (the big cheese pile). Everytime it runs over 'a' or 'b' it adds 1 to the A or B accumulator. 'A' and 'B' do the same for subtracting. 'T' only allows turning left if the B accumulator is 0. 'P' places the A accumulator onto the stack, 'R' outputs the entire stack. There's a few more instructions that are not quite as important.
It's quite a fun and simplistic language (not turing complete in my opinion, due to lacking stack manipulation) that has a few more tricks to it than you might expect at first sight. The challenge of keeping the rat fed is pretty funny and learning how to golf your code is super interesting.
Review: 8/10 you should give it a try at least once (but I'm biased for 2D languages)
The only metric that matters LOL