While it is "just" a tower defense game, I give it originality points for giving the enemies pathing and letting you use your "towers" as walls. I know this isn't a new concept, but it makes it much better than the usual approach that people do where they just have a fixed path for enemies.
I also like how each "tower" was a different Ironmouse model, and the deckbuilding gave a little bit more depth.
I did find it rather easy though-- the basic strategy of keeping a number of cheap cards to wall out the enemy meant I never even came remotely close to taking any damage in the first 4 levels, even without needing to buy upgrades for the mouses/towers. I didn't finish the 5th level because I accidentally refreshed, and it didn't save my progress, which is an unfortunate bug. A fast forward button would also be greatly appreciated. Without that, I didn't really want to go through all 4 levels again to get back to where I was.