osu! is primarily played using a mouse to click 'beats' displayed on-screen in time with the music. This is analogous to tapping the beats on the Nintendo DS screen with a stylus. At the top of the screen, a health bar is present, which is constantly drained. If the player hits or clears a beat, the health meter at the top of the screen fills slightly. If he misses a beat, a large part of the meter is drained, and if it gets completely empty, he fails the song. There are three types of beats in the game: Hit circles, sliders and spinners. Every time the player hits a hit circle or an end circle, touch a slider tick, or clear a spinner, the combo is raised by 1. If he misses any of the above, the combo is reset back to 0.

osu! is now beyond its time in many areas, with a huge focus on web integration and community aspects. Features are added based on people's requests, and their perceived usefulness to the community as a whole. The map submission process (Beatmap Submission System) is seamless and intuitive from start to finish. Importing songs, loading skins and playing the game is simple enough for almost anyone to handle.
Multiplayer support is available. New gameplay modes are implemented to expand the scope of this game beyond its original expectations.

I hope that's enough information, sadly I couldn't find a wikipedia page or more info about this game.

This game is REALLY hard, as it involves fast clicking and mouse movement.
But, it is fun.

Not to be a lazy douche but, could you put up links and videos?
System requirements would be pretty neat too, since no one in this board like to list them haha.

System requirements:
1GHz+ Processor
512mb+ RAM
Microsoft .NET Framework (2.0+, 32bit)
also, the official website is http://osu.ppy.sh

Anyways, I used to play this game a few months ago, and since you reminded me of it, I'm in the mood to start playing again. Username is Daxxtah if you ever end up making a list.

Played this with rittu and ishi a long time ago, great game and has a lot of songs you normally don't hear. (anime OST's etc :3)

I don't expect it to be high, since it works on my Mac, And my Mac has really bad specs...

It's a great game, but hard to be really good at it. I can't do anything harder than a "Normal" song :P

Played it ages ago.

It's better played with a DS and a stylus in my opinion.

do we can download it free? sounds interesting...

Yes, it is free, no paying whatsoever.

@Darke, you can play it on an ipod if you jailbreak it. That may solve your problem.

this game is hard lol

im fireless in it