In Patapon, you play as a god. You command an army of little eyeball men, the titular Patapons, to cross horizontally scrolling screens and destroy various enemies and structures. The way you command them is what makes Patapon truly unique: you beat various rhythms on drums (represented by the PSP's face buttons). Each of these commands is done in exactly four beats and is carried out on the next four beats. The game is carried out in real-time but you can only issue commands w/in this structure of beats and commands cannot be changed or canceled once given so it ends up having a bit of a turn based feel as well. You start out w/ basically only the commands for attack and advance but as you progress you learn commands for retreat and defend and eventually a few special commands that can to control the weather in order to provide certain advantages to your army. You are rewarded for keeping a steady rhythm by going into what is called fever mode in which your army's attack power is greatly increased. Keeping this beat can be frustrating for some but most will get the hang of it after a short while.
With only a few commands, the strategy elements of Patapon are fairly light. However, there is a good deal of depth to the game because you get to build your own army. You can add new Patapons to your army by collecting various items and ka-ching, which is the game's unit of currency. Additionally, various enemies drop weapons and other upgrades and you can customize your army's equipment down to the individual unit. There are a half dozen different kinds of units and between them you can generally come up w/ more than one strategy to beat most stages. Unfortunately, you can also just build up your army to the point where you can storm through many of the stages w/o using any kind of strategy of all.
The stages are all still very fun to play. The stylized silhouette-like graphics are sure to be timeless and the way that music is integrated is second to none. Your army and enemies are artfully created w/ a great sense of humor and boss designs especially a large and very striking. The design here is so nice, that it's practically as much fun just to watch videos of gameplay as it is to actually play--not that I would want to give up the latter myself.
The only major problem w/ Patapon is some gameplay elements are not described well in-game. The rhythm required to do certain commands--the ones that change the weather--is never described sonically just through a visual (and somewhat inaccurate) representation on screen There are also a few items that need to be acquired through random enemy drops that can be annoying, esp. since you are sometimes not told where to get a given item or even that new item is needed at all. I personally wasted quite a few hours building up my army on my first playthrough when what I really needed was to go back a few stages and pick up a few items and learn a new command. The end result of this was an overpowered army for the remainder of the game. These problems are pretty minor overall and only end up being a hindrance a couple of times over dozens of hours of gameplay.
Ultimately, the good far outshines the bad w/ Pataopn and if you're not charmed by its unique gameplay in quirky premise, I'm not sure you like video games at all. Patapon is a unique experience and if you have a PSP, you owe it to yourself to at least check out the demo.