That's crazy.

I'm so confused as to how an invalid level value would generate a level with all sorts of bizarre, invalid combinations... yet still be completely playable, without crashing or anything.

In 2011 I wrote an emulator for the LatticeMico32 processor [1]. After it was written, I decided to play the chaos monkey game and change some instructions, like reversing "less than" and "greater than", just for kicks. So the code I was actually running would be the equivalent of taking a program and replacing all > with < (and vice-versa). Much to my surprise, some emulated code still worked. It mostly did the wrong thing, but the fact that the code worked, printing stuff in the screen and all, still baffles me.

[1] http://www.ubercomp.com/jslm32/src/

It can and does crash a bit, as noted on that video.

9-2 looks like Flappy, a couple decades earlier.