It uses a cross-platform game-programming library called
Allegro, which finally supports the Mac well. So the process of porting was something like this:
1. Compile and install Allegro on my Mac.
2. Figure out a couple more things about XCode, frameworks and stuff. (I'd used it before, but I learned more useful things from doing this.)
3. Replace the sound library FMOD with BASS. (The version of FMOD I'd used isn't available for OSX and the new version is quite different, so I chose to go with BASS which I have used a bit before.)
4. Replace a few Windows-specific assumptions and functions, and replace some deprecated Allegro functions. (The code was already mostly platform-independent C and pretty clean, so this was an easy and quick step.)
5. The game finally compiles and links... and runs!
6. Test the game. - Discover two small bugs in Allegro's OSX code.
7. Get the bugs fixed. (One of them - one of the sticks on my gamepad didn't work as expected - I actually was able to fix myself and send in a patch for. I'm proud of that.)
8. Test the game some more.
9. Learn how to package a Mac app, and put it in a nice-looking dmg complete with a new icon for the app and a background image for the dmg. (Including making some silly mistakes in the process, of course, but I really like the neatness of the .app and dmg packaging of things. That's something Apple has done well.)
10. Release it.
It took me a week, with plenty of time included for practising tuba, reading, lawn-mowing and so on. A guess might be that I spent 15-20 hours in total on it. Including the testing and learning.
