I'm glad you liked it! You have to hit the boss in the head, which isn't very obvious. I'll have to tweak that somehow.
You're correct, the AI for most enemies is pretty simple. I do have plans for more advanced AI like the skeleton for later stages. This is the first stage, so we didn't want it too difficult.
I can see that subweapon switching might be an issue. You can't pick up the old one for a few secs, which I thought was enough. I'll have to think about that more.
I agree with you, there's not much reason to kill the enemies. I plan on adding some random drops when they die, like invincibility and maybe health. BTW, there are hidden health drops if you can find them!
I can add in mouse bindings as well. I wasn't sure if anyone would want them.
Thanks for all the great suggestions, and taking the time to write them up! I appreciate it!