[ WHAT IS "OSU!"? ]

According to the main osu! page, osu! gameplay is based on a variety of popular commercial
rhythm games. While keeping some authentic elements, osu! adds huge customisation via
skins/beatmaps/storyboarding, online rankings, multiplayer and boasts a community with over
500,000 active users! Play the way you want to play, with your own music, and share your
creations with others.

[ HOW DO I PLAY? ]

First, go download the game!

There is a tutorial included, but here's the basic run-down of the different game mechanics, provided by the Wiki page.

Game levels are called beatmaps. In each beatmap, a song will play and different rhythmic hit
elements (hit circles, sliders and spinners) will appear on the play field. Players must use a
pointing device to manipulate these elements in time with the playing song's rhythm in order to
earn points. While the mouse is considered the most popular input device, combinations of
mouse, Tablet PC, graphics tablet and keyboard can be utilised.

Difficulties
There are 4 default difficulties which are easy, normal, hard, and insane. There is also a
marathon difficulty that means maps are over 5 minutes of drain time.

Objective
The main objective when playing osu! is simply for players to hit, complete, and clear enough
hit circles, sliders and spinners to keep their health bar, which drains at a steady rate
throughout the game, above 0 until the song is over. More experienced players will often strive
for a more specific and difficult goal, like improving their high score or grade on a particular
map, usually by attempting to time their hits better and avoid as many misses as possible to
increase combo multipliers.

Hit circles
Also sometimes referred to as notes, hit circles are a common object on nearly every beatmap.
When a hit circle appears, a ring, called the approach circle, will appear around it and begin to
shrink. In order to score points from a hit circle, players must place their cursor over the circle
and click the hit button as the approach circle touches the edge of the hit circle.


Sliders
Sliders appear as two hit circles with a solid path, called a slider track, between them. As with
hit circles, an approach circle appears at the beginning of a slider track, which must be clicked
when the approach circle touches its edge. Unlike hit circles, however, after the start of a slider
has been hit, a ball, called the slider ball, will begin to roll along the slider track, and players
must continue to hold down the hit button and keep their cursor hovered over or near the slider
ball until it has reached the end of the slider. Sometimes a slider end will have an arrow, which
means the player will be required to follow the slider ball back to its starting point.

Spinners
A spinner is a large circle that takes up most of the play field when it appears. A ring like the
approach circle of hit circles and sliders will also appear and begin to close on the spinner's
center. Players must hold down the hit button and spin their cursor about the center of the
spinner. As players continue to spin, the spinner gauge at either side of the screen begins to
fill, and once it has been filled, the player will be notified that the spinner has been cleared.
Continued spins after this and until the ring reaches the spinner's center will award bonus
points.

Hits and misses
Hit circles, sliders, and spinners have different criteria to how they can be hit or missed, and to
how points can be gained.

Clicking the hit button at the right time while the cursor is hovered over a hit circle or the start
of a slider, or clearing a slider will earn a player points. In the case of hit circles, the points
awarded are completely dependent on the timing of the hit. Sliders are generally considered
more lenient, and as long as a player doesn't hit the start far too early or too late, collects all
the slider ticks, and continues to hold the hit button and hover the cursor over the slider ball
until it reaches the end, a maximum number of points are earned. The points awarded by a
spinner are dependent on the number of spins completed. Additional spins after a spinner has
been cleared will further increase the points earned. Successful hits will fill the health gauge a
small amount.

No points are earned when an object has been missed. Hitting a hit circle too early or too late,
failing to either collect any slider ticks or finish the end of a slider, or failing to fill the spinner
gauge an adequate amount will result in a miss being added to a player's score. A miss, or
missing a slider tick, will cause the health gauge to drop a small amount.

Scoring
A combo multiplier is kept throughout the song. Upon successfully following an object (hitting a
hit circle, hitting a slider end or slider tick, clearing a spinner, etc.), the multiplier is increased
by 1; upon a failure (missing a hit circle, missing a slider end or slider tick, not filling a spinner
an adequate amount, etc.), the multiplier is reset to 0. This multiplier is then multiplied by
several factors including the difficulty of the played beatmap and "mod multiplier", user-
applicable multiplier resulting from activating gameplay-altering mods, which is then multiplied
by the base score of the hit to get the score of the hit. To be more precise, the score formula of
a hit is:

Score of a hit = Base score of a hit * (1 + combo multiplier * difficulty multiplier * mod multiplier / 25)

[ GOOD GAMEPLAY VIDEOS? ]
Here's some examples of the skill level of some of the people who play this game.