Mobile Recommendation (from me, shocking, I know):
Terra Battle:
http://www.neogaf.com/forum/showthread.php?t=909650
Terra Battle is a free-to-play mobile game by Mistwalker. It features game design by Hironobu Sakaguchi and music by Nobuo Uematsu, both of Final Fantasy fame, and artwork by Kimihiko Fujisaka, of The Last Story and Drakengard fame. Other well-known artists are scheduled to contribute content according to the Download Starter.
Its an SRPG Puzzle hybrid and just plain fun. Plenty of depth and challenge to the positioninging aspect which works as pretty interesting puzzles that are as hard as you want them to be (more on that later) and the general RPG grind/upgrade hook. The game is free to play, but it really seems like you dont need to spend money to get something out of it. Additionally, you get 5 free energy after the first chapter (5 missions) and 5 more if you enter the code "dhth66nWXVCbjdTC" in the game. Took me 2 rerolls (deleting game data via settings on android, NOT the install) to get a few decent chars from my free rolls and been playing since then.
This is what you'll be doing most of the time:
Every turn you can choose one of your characters, which you need to position strategically on the board. If you corner an opponent with 2 of your units, they attack and make damage. However, there is two things to consider here (going back to the "as difficult as you want it to be"-thing, which actually make this very fun to play):
1. You get bonusses for lining up your characters during an attack, meaning you always need to keep in mind all of your characters for the best attack/support combos and successfully planning and pulling off a combo with all of your characters feels VERY rewarding.
2. You can only move one character every turn, BUT you can affect your other characters during your move, effectively pushing away your allies to get them in a good position. This leads to a lot of possibly strategies and positioning changes before you start the attack and is a very rewarding puzzle to figure out.
Lovely game, recommended.