I wrote a game in PL/M in the bad old days before good debuggers. Didn't work. Fast-forward and years later a colleague wrote a source debugger for our OS (CTOS

I wrote a game in PL/M in the bad old days before good debuggers. Didn't work. Fast-forward and years later a colleague wrote a source debugger for our OS (CTOS) and in half an hour I had the game running. Bad pointer construction if I remember right - pointing to byte variables and treating them as pointers to words.