Thanks a lot for the encouragement! I do have plans for updates on this game in the future, with more levels and weapons.
Multiplayer is currently low on my list though, as that would involve a server and complicated network stuff. Would LAN multiplayer be good for you? As that would be easier to implement.
Again, I really appreciate your enthusiasm for my games, but please don't post multiple comments about the same matter, because that would make it harder for me to read all your comments.