Began adding the music and sound systems to MGS. They're implemented as separate systems, because one needs to play one thing all the time, whereas the other needs to play all the things one time. Since I'm building the game with an entity-component-system design, it's fairly easy to add new things quickly, but it's slightly harder to make sure each piece of the game only does the one thing it needs to. And does it right.

But at least with an ECS design, it's also easy to tear things out and replace them, so I'm not too worried about getting everything perfect at the moment. Maybe after I get the audio working, I'll add some level generation, or AI to the game. Hmm, decisions, decisions...