Nightfall has been out for a couple of years now on iOS, but was always one of the pricier games - at least at that time. Since then it has come down in the form of good sales, and I nabbed it after one such special and gave it a go.
It seems like many CCG titles for mobile devices are free to play, and try to hook you so you will spend money on more stamina/turns or packs of cards. Here you do not feel that push as you buy - and then play - the game.

Chaining cards together and sorting through the stack feels very familiar to a fan of Magic: The Gathering. The phrase first in, last out (or its opposite, last in, first out) seem to apply.
The tutorial is lengthy, but you will want to follow it. Otherwise you may well come out of the gates very confused as to how the game itself plays. Once you understand how the game plays though, the interface does its absolute best to stay out of the way. You can slide cards easily, rotating the fields of play quickly to find what you need. There are online and offline modes, and while the former are more fun, I did have a little trouble finding matches at times - likely due to the age of the game and that there are newer and shinier CCGs out there.
All in all, I had a lot of fun with Nightfall, and would score it a 7.5 out of 10.