Pretty fun game, although the transition from killing inviting people to collecting more invitations felt a bit frustrating (and perhaps having no invitations left should give a bit more feedback).
Took a bit of time to figure out the joining part, had no issues separating though.
The graphics are and sounds nice but lacked some animatons (although you did a good job on particles).
Oh, I just remembered one more thing: I wish there was a death animation instead of abruptly switching the screen.
All of the above might be nitpicking, great job nonetheless!
UPD: I'd suggest adding a couple screenshots to your game page. Honestly, I felt a bit hesitant to play your game without these. Probably it was due to a lack of a web version though, but screenshots are always welcome.