I really enjoyed this game, graphics were excellent (apart for the way the characters seemed to constantly need the toilet...) gameplay simple to understand, story with more twists and turns than a Norfolk bypass and battles tricky enough to hold you for the 3 minutes they last.
Basically you play Lock, a young man aspiring to be an Archineer like his parents. Archineers are the people who build the walls to defend the city against the evil clockworks.
You start with roughly 2-5 minutes (depending on the level) to build up walls, traps and towers, built using "source" and bits of scrap you ifnd during battles. The Tutorials are in game and its very easy to get the hang of, but designing some of the towers/traps etc can be a tad tricky, but nothing too difficult.
You then go into a 3-5 minute battle in which your walls and your own fighting power have to hold off the oncoming Clockworks. You can repair the towers and walls, but not rebuild them so multi tasking is essential to keep them upright until the battle is over.
As you progress you get stronger walls, traps, towers and helpers, but the enemies also become stronger and stronger and more varied with everything from flying ones, to ghosts!
Its also got a brilliant story line which has you guessing right up til after the credits have ended.
I have been told the multiplayer is excellent, but haven't tried myself.
I would advise this game to anyone who enjoys games like the battle and defense side of Age of Empires, although no where near as advanced and complex it has similar qualities and is good for picking up and doing a level whilst on a break from everything else. Not being so complex you can then put it down again!
My only problem is how short the game is and the lack of sandbox mode. I'd like to see something where you build the best denfense and see how long you last rather than have to hold out for X time. The game is only 100 levels of 10 minutes total max, I bought it 4 days ago and have completed it already.