Okay... Needs some additions and improvements.
Great game although there are a little things that could be helped to make it better. First of all fix the darn lousy return to lobby button. I keep having to exit game, reload, log in, and start playing. Fix that and im sure a lot would be happy. Second. As shinkled said "there needs a way to change the speed of the game play", with out affecting the timer to build. That way you get the same time to build but faster and more action out of the game. Third. An option you could add would be maps with unmovable blocks so you have to build around them. Etc. Another addition that would be nice is a raking system, for ranked unranked games, possibly a skirmish/sandbox game play, and you should have a complete well done game.
P.S. the Sandbox should also be able to work with multilayer to see which TD is better than the other without having to go though all the levels. And it should only work with unranked games.