In case you're interested, I've just added some new powerups into the game like you suggested. There's now a shield, a shotgun-like upgrade, and an explosive bullet upgrade (and of course I'm keeping tripleshot). They're ridiculously unbalanced at the moment since you can stack them (my highscore went from about 45k to over 100k), but I'm thinking of adding a battery and radar shop upgrade to counteract that (the radar would affect the rate of upgrades appearing, and the battery would affect powerup time limits). Still haven't gotten around to autofire or enemies, but I figure this is a good start.
Also, I finally figured out shaders, which is why the background it different.
Thanks again for your recommendations!
