-Large variety of enemies
-Liked the autofire
-The ability to power the ion cannon added a necessity for skill into the mix.
-No upgrade system? The game would have been much improved with an upgrade system, which I was surprised to find it didn't have. Without upgrades, the game gets boring, and I felt that an upgrade system would have held my attention longer.
-The lack of variety in powerups (only five--laser, dual shot, triple shot, rocket, and healing) was disappointing, especially given that there was no upgrade system.
Otherwise, decent game, and I look forward to a sequel (with either a lot more powerups or an upgrade system)