The iOS version of Star Realms is a sound
adaptation of the card game with some of the best online features I've seen in
equivalent apps.
Star Realms is a deck-builder which focuses on a two-player experience and a simple card-combo system. You can think of it as like the the core version of Ascension, before it got bogged down with loads of unwieldy expansions.
The app also has a fun campaign for a greater variety of matches
and AI opponents (though they are not very challenging). I've sunk a ton of time into this little game, so it comes highly recommended from me.
Expect a review of the physical game in the near future.