A nice tower defence game that I recently encountered is AI conflict.
The game is set in space and lets you battle multiple ‘AIs’ (of course they don’t fit the meaning I attached to them in my previous post). You can configure each tower in a very detailed manner: which enemy to attack, how to cooperate in group, etc…
Anyways, it is one of the better tower defence games that I’ve recently played.
Additionally, it’s made in HTML 5 which means you can play it on any platform (such as your tablet)!