Pretty cool...
In the future, you might want to include some kind of tutorial, level system, goals...
Maybe increase the missile/torpedo drop... Let's see...
Homing missiles would have been quite useful. Maybe a multishot type of laser (kind of a wide spread shooting type)...
Lets see... set up permanent upgrades instead of having only temporary ones, allowing you to build up meaner and bigger bad guys, possibly great big bosses.
hmm... what else... music switch off option... different weapon sounds (put into a random setting) would give it more interesting firing sounds.
Thats about all i can think of right now.
Good luck in the future! This little game was pretty fun the first few times to play.