The most interesting thing I've found so far is the anti-tampering mechanisms.

In Time Pilot - there are three routines that are called constantly from inside the main loop. Each routine computes the checksum of the other routine's code to see if it's been modified. If so it jumps into random junk data.

There are other less exotic routines that make sure the copyright string hasn't been modified, etc.

https://github.com/qarl/arcade-js/blob/main/games/timeplt/id...

Fascinating.