So this isn't called Asteroids. It is in GitHub, however. It really isn't like Asteroids, anyway.
Game aficionados will notice that I'm not really playing, I'm trying to break it (that's my excuse, anyway). I also made my ship immortal for the video. No sense losing on camera...
This wasn't meant to be a complete game, just to get an idea of what could be done on this display. The extra dots created by the upsampling DAC look like little comets or bits of space junk on the screen, and aren't that distracting. In another game genre, they might be a problem.
I also wanted to test integration with SDL2. In this case, SDL2 is just used for joystick events. You could also use it to add sound to games using another audio adapter. One issue is that when SDL is used without a video window (arguably not a use case it was designed for), it doesn't process keyboard events.
The joystick (gamepad) I've been using is a Buffalo iBuffalo Classic USB Gamepad. Here it is connected up with the Pi and the SYBA audio adapter, running off of battery power: