Where to begin. If I wanted to treat this game punitively, I'd say it takes the standard Final Fantasy team line-up (warrior, black mage, white mage, archer) and they've thrown in a puzzle game). I can't be that punitive. This game has complexity, and depth you'd struggle to find in some of puzzle games you'd immediately think of.
You have four lines across the screen, gems will slide towards you, if they reach the end, they disappear. If you move 3 of the same colour in any pattern except diagonally, you can make an attack gem. Which, when clicked, will attack the enemy you are fighting. The enemy has their own gems too, if you can't move them quick enough, or can't use your attacks to remove them from the bar, they will attack your characters and drain their health.
And I'm only getting starting. Characters level up between runs, learn abilities, monsters, mini-bosses, runes that make the game move faster, or randomly freeze different runes, or make you take more damage.
Oh, one thing I didn't mention. This game is tough. It starts deceptively simple, but it works through it's mechanics like Neil DeGrasse Tyson blows your mind.
It has different modes of play, an easy to grasp tutorial level, and a very FF-esque art style (think DS remake FF games).
The only thing I can even think to ping this game for, is the soundtrack is incredbily repetitive. You might do better to listen to your own tracks and turn the music off entirely.
The best part? This game costs under a dollar. Seriously, less than a small fries from McDonalds. If you've been looking for a rich, deep, and challenging puzzle game. I implore you, pick this up. You will have an absolute blast.