Absolutely fantastic concept for a game - a first person shooter tower defence. I am a fan of both genres even though my skill at both are apalling.
The concept is great, however the game itself appears to try too hard in some aspects - I like to think I have an above-average quality gaming laptop but sanctum is considerably laggy and almost impossible to kill things in.

Yes, it's a fantastic game - but I may not be the best person to ask of an opinion for as I suck at these sorts of games and the lag does not help - if you have a good PC, and if you like these genres then you definitely should try it out.