Controls on this shooter are arrow keys to move, Shift to spend upgrades, and X or space as fire keys, Z for special weapons. However, in all emulators I tried, Shift won't actually apply your energy to weapon upgrades. As such, you're stuck taking the top option upgrade when it maxs out. Gameplay is reasonably generous (your ship is pretty durable, and there's not a lot of bullet hell) but it does delight in enemies (and even bosses!) who attack from behind. This game uses some kind of custom DOS, and doesn't appear to run on Anex86 at all, so try NP2 or T98-Next.