Think WarioWare, but longer play time, and overall more fun.
Basically, you start off with a simple rhythm game. You have to ping a building block onto a conveyer belt in time to the catchy music. You do this by a flick of the wrist on the touch screen. Sounds simple? It is. But it's a suprisingly awesome idea. But unlike WarioWare's ridiculously short microgames (lasting about 5-10 seconds), Rhythm Heaven's games last for around a minute or two.
Many more of these games are unlocked as you reach 'ok' scores on the last available game, from gardening to drumming to photography to DJing! And all of these have ridiculously catchy music in the background that you will find yourself humming along to outside the game.
There are also mini games and rhythm toys to play with when you collect a certain amount of 'superb' medals which are all great fun.
However, the only bad point of the game is the easyness of the games. Anyone who can tap their foot to music will find this a breeze, but that doesn't stop it being a great game. Highly reccomended!