I got to wave 48/50 on medium on my first try... dog spazzes out repeatedly hitting my mouse and i die. [5/5] regardless of the dog thats now sleeping on the floor.
Hit tab so it highlights the Weapon at top left corner, hit enter so it opens up weapon list, use arrow keys to pick the weapon you want and finally enter to select it. + so people see.
I was going to make a comment about not being able to use the second weapon slot. Then I upgraded my ship, lo and behold it unlocked the second slot. Fun game regardless [4/5] (Would've been nice if you'd told us you have to upgrade the ship to unlock the extra slots).