VHack API
I reverse engineered this game back in 2016 and it was the very first time I reverse engineered any API/software at all.
I ended up building a library in PHP to access their API and a bot using PHP and CRON jobs to automate its activity.
I did this by mainly looking at the
HTTP requests the game sent over the wire so it was not anything special requiring any decompiling and deciphering.
My reverse engineering efforts actually helped securing the game because shortly after the owner added a rather basic yet effective cryptographic signature verification for each HTTP request.
This signature verification is still being used even in his newer games which I reverse engineered later. (VHackOS, same premise as VHack except it was a mobile-hacking context instead of a desktop-hacking context)