Its an Awesome game, but could've been longer.
The gameplay is simple, using only the A and B buttons most of the time, along with the control pad to move the slime dude around. Unfortunately, there is little to no use of the touch screen whatsoever during the game. During battles, you command a tank (which looks like the slime dude) and throw stuff into the cannons (or you can jump into the cannon and pray that you survive the enemy's lobbed ammo :P). Very simple, but it gets strangely addicting.
As with all Square games, the music fits into the game well at all times, and gives it an adventurous, yet innocent feel. It is quite innocent, since you play as a gooey slime that bashes into enemies that seem to offer no resistance at all. Fun.
All in all, it's a great game that offers a fun twenty or so hours of addicting and simple game play. The only bad part I can see about this game is that it only has one game file to play on...