I have to admit, I was not expecting to have as much fun with this game as I did. It's a kids game targeted at children ages 6 - 8 or so, and this review largely is as well (or moreso: any parents reading this)
The game is polished & adorable, with bright colors, pleasant music, and cute monsters that are largely nonthreatening and quite imaginative.
At its core it's a puzzle game using pretty much the most basic of addition/subtraction- and while the difficulty/complexity of the math problems never really increased, it would have felt out of character for the game to do so.
The gameplay is solid & bug free, with a simple premise (matching the values of monsters on the field with "spells" in your spellbook. You can modify the values of the monsters, and add your spells for greater sums to be used in combos, not as a requirement- just for a higher score. Though clearing 7 monsters at once with a well placed spell is fairly satisfying, even as a 24-year old adult.
It's fairly long too, which is a pretty nice plus for a $4 game.
If you have kids learning math, I'd highly recommend this one. It's pretty easy to pick up, no stress, and just as fun as any of the more mindless apps on the market (Angry Birds/Temple Run, that kind of time vortexes.) Seriously, I would have loved to play this as a child, and still had fun with this as an adult. So if you're an adult that's bored and would like a time-waster, this is actually a fairly decent/low-commitment game as well!
I also did a video review if you'd like to see gameplay/more in-depth impressions (kid friendly): http://youtu.be/QVl0dvIv3zQ