Good game, needs some work
It's a GREAT start, and with a little more work could really be a cool game. I think it needs some additional sounds, and perhaps a timer or something. There's no sense of urgency. It's like "Hey these mutant alien things came over to my home base for tea, and while they wait on the other side of the room I'll kill them all." =)
Keep at it and with version 1.5 I'm sure it'll rock!