FTL works really well with a touch interface. My iPad was just an FTL machine for quite a while.
If you like hard roguelikes, this one is a winnner.
On a separate note, several of my games, like T&E, Can't Stop, and FTL, pop up that warning that they may slow down my iPad. That means they were never updated to 64-bit, and rumor has it that as of iOS 11, they will no longer run. I guess I won't be updating my iPad if that turns out to be true. Just a heads up.
Card Thief is BRILLIANT. I think in terms of original IOS card game designs, it is the best.
It is somewhat hard to get a handle on at first...I wasn't very impressed to begin with myself. But when I realized how efficiently it does, as Vlad suggests, capture elements of Thief in a 3x3 card grid, it blew me away. It is all about opportunity and risk- when to take either- and working out how you are going to make it past guards, get behind them for backstabs, avoid traps, avoid light, and have enough stealth to pick up the treasure...which you can let sit and get more valuable.
There are so many brilliant touches to the design- like how you can clear a full board and get all of your stealth back, but it also puts eight new cards out that you may not be in a good position to handle. The way guards "see" is just genius, and the game adds some interesting wrinkles to that. Then you've got equipment cards that you'll agonize over using or waiting for later. And how the number value of cards works is just so smart. It could totally work as a physical tabletop game, a solo game, but it would require a level of admin that would make it undesirable, I think.
I haven't even made it through the second castle yet but the daily challenges are fun and trying to beat your best scores/highest chests is fun.
All in all, it is the only IOS game recently that I've been truly blown away by.