osu!

osu!
File:Osu!Logo (2015).png
Developer(s)	Ppy Pty Ltd
Publisher(s)	Ppy Pty Ltd
Designer(s)	Dean Herbert
Platform(s)	Microsoft Windows macOS (pre-High Sierra) iOS Windows Phone
Release	September 16, 2007
Genre(s)	Music
Mode(s)	Singleplayer, Multiplayer

osu! is a freeware rhythm game developed and published by Australia-based company Ppy Pty Ltd, created by Dean Herbert. Originally released for Microsoft Windows on September 16, 2007, the game has also been ported to macOS, and Windows Phone. Its game play is based on commercial titles including Osu! Tatakae! Ouendan, Elite Beat Agents, Taiko no Tatsujin, Beatmania IIDX, O2Jam, and DJMax.

osu! is written in C# on the .NET Framework. On August 28, 2016, osu!'s source code was open-sourced under the MIT License, the game's assets are under the CC BY-NC 4.0 Creative Commons license. Dubbed as "osu!Lazer", the project aims to make osu! available to more platforms and to provide transparency. The community, as of March 7, 2018, has gained over 11.68 million registered users and 7.70 billion ranked plays.

Gameplay

The player chooses a song and a difficulty from a list of downloaded "beatmaps" or "maps". As the song plays, the player must click (or use the alternative keys Z and X, which can be adjusted in the options) on different hit-elements (hit circles, sliders, and spinners) in time with the rhythm of the song in order to earn points. This is commonly done using a mouse, although more experienced players tend to use other input devices such as a graphics tablet or touchscreen.

Difficulties

There are five default difficulties which are defined throughout the game as Easy, Normal, Hard, Insane, and Expert (also commonly called Another and Extra). Other difficulties exist for special cases, namely Marathon, for maps exceeding 5 minutes, and TAG, designed for a type of multiplayer gameplay where players must take turns performing parts of a map. Content creators may choose to name their difficulties anything outside of the standard naming conventions, as long as their names imply their appropriate difficulties.

Objective

The main objective of osu! is to clear a beatmap while preventing the health bar from draining fully. This is achieved by hitting the hit-elements as they appear to the song's rhythm, which will replenish the bar accordingly. More experienced players will often strive for a more specific and difficult goal, such as acquiring a better high score or rank on a map by improving the timing of their hits, avoiding misses to maximize the combo multiplier or applying difficulty-raising modifiers in exchange for score multipliers.

A hit circle as it appears in the osu! editor.

Elements

The elements of osu! are hit circles, sliders, and spinners.

Hit circles, also known as notes, 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 closes and disappears under the hit circle.

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, called the reverse arrow, which means the player will be required to follow the slider ball back to its starting point.

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

In osu!Lazer, the approach circle is replaced by the changing of the color of the border of the spinner that gradually fades to red as the spinner approaches the end. The gauges are also absent. The new spinner also has 3 parts, that all move at different speeds when spun.

Hit circles and sliders can be any color.

Scoring

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 collect any slider ticks, 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 or end, causes the health gauge to drop an amount.

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 fault (missing a hit circle, pressing a slider start too early, missing a slider start or slider tick, not holding as a slider ball hits a reverse arrow, or failing to spin a spinner an adequate amount), the multiplier is reset to 0; the combo multiplier is not reset to 0 by missing a slider end, nor is it increased for receiving any bonuses from a spinner. 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 + Base score of a hit * (Combo multiplier * Difficulty multiplier * Mod multiplier) / 25

Base score of a hit	The hit circle judgement (50, 100 or 300)
Combo multiplier	(Combo before this hit – 1) or 0, whichever is higher
Difficulty multiplier	The difficulty setting for the beatmap
Mod multiplier	The multiplier of the selected mods

Additionally, each slider start, end, and repeat tick awards 30 points, each slider middle tick awards 10 points, and each rotation of a spinner awards 100 points. Players are also awarded with additional bonus of 1,000 points for each rotation of a spinner after the spinner meter is full.

Mods

Difficulty reduction

These mods reduce the difficulty (for example, by disabling failing so a player can play even when the health bar reaches zero), but at the expense of reducing the score multiplier.

• Easy (abbreviated as EZ) reduces the value of Approach Rate, Overall Difficulty, and HP Drain by 0.5, as well as increasing the circle size. Also, the player is given three lives; that is, when the HP bar is exhausted, the game pauses and it refills up to two times. This mod multiplies score by 0.50x.
• No Fail (abbreviated as NF) makes the player incapable of failing at the expense of a 0.50x score multiplier.
• Half Time (abbreviated as HT) decreases the BPM (beats per minute) to 75% of its original value, and increases length of the song by 33%. This mod multiplies score by 0.30x, except in osu!mania gamemode, the score is multiplied by 0.50x.

Difficulty Increase

These mods increase the difficulty of the map in various ways, and reward the player with an increased score.

• Hard Rock (abbreviated as HR) increases the value of Approach Rate, Overall Difficulty and HP Drain Rate by 1.4, while decreasing circle size by 1.3, mirroring the map vertically. This mod adds a score multiplier of 1.06x. In Catch the Beat gamemode, the score is multiplied by 1.12x.
• Sudden Death and Perfect (abbreviated as SD and PF, respectively) causes HP to instantly drain to 0 if certain criteria are not met. In Sudden Death's case, the map is failed if the player ever misses, hits the beginning of a slider too early, or otherwise breaks combo. Perfect mod fails the player if their accuracy ever goes below 100%. These modifications do not affect score.
• Double Time and Nightcore (abbreviated as DT and NC, respectively) increase the BPM to 150% of its original value and decrease duration of everything in the beatmap by 33%. Nightcore also increases the pitch of the song and adds a rhythmic beat. In original and Taiko gamemode, this mod adds an extra 1.12x multiplier to the score. In Catch the Beat gamemode, the score is multiplied by 1.06x.
• Hidden (abbreviated as HD) removes approach circles and causes hit circles to vanish a period of time after appearing, based on the beatmap's set approach rate. Sliders vanish over time as the player continues to follow the slider track with their cursor. The player still has to click on the correct position of the note at the correct time to score a hit, as in standard play. In osu!taiko, Catch the Beat, and osu!mania, notes disappear about halfway through the screen. Like Hard Rock, this multiplies the score by 1.06x.
• Fade In (abbreviated as FI and available only in osu!mania) is an inversion of Hidden, making the notes fade in as they reach the bottom half of the screen. This mod doesn't add any score bonus.
• Flashlight (commonly abbreviated as FL) causes the screen to go black, except for a small area around the cursor. The visible area becomes smaller at 100 combo and again at 200 combo, returning to its original state if the combo is broken. This mod adds a 1.12x multiplier to the player's score.

Special

These mods are the mods that don't apply to other categories. These mods make the play "unranked" and scores achieved while using these mode are not recorded (excluding "1K"-"9K", "Co-op" and "Spun-out" mods).

• Relax (unavailable in osu!mania & osu!taiko; abbreviated as RX) requires the player only to move the cursor, while the notes are hit with perfect timing automatically. It is impossible to fail in this mode. In the Catch the Beat gamemode, this mode allows the player to use their mouse to control the character.
• Auto Pilot (osu! standard only; abbreviated as AP) causes the cursor to move automatically so that the player only needs to click. using this mod you cannot fail.
• Spun Out (osu! standard only; abbreviated as SO) makes the game automatically complete spinners for players. Using this mod results in a score multiplier penalty, thus creating a 0.90x score multiplier.
• Auto allows the player to watch a perfect play of the beatmap (with some exceptions).
• Cinema shows only the background and storyboard, while automatically playing hitsounds on time. It is possible to use Double Time, Nightcore and Half Time alongside this mod. Background dim will be set to 0%, and background video and storyboard will be tuned on while this mod is in effect.
• xK (osu!mania only) will force all osu!mania beatmaps to use the selected key setting, ignoring the original key setting of the beatmaps. It is possible to choose key settings from 1K to 9K. This mod reduces the score by 33–10%, depending on selected key setting. If selected key setting matches the original, score is not changed. This mod does not work on any beatmap that was specifically created for the osu!mania gamemode.
• Co-op (osu!mania only) introduces a second playfield with second set of controls based on current key count (e.g. 7K -> 7K + 7K). For osu!mania specific maps, the key count is split in half, while on maps with odd key count, one set of controls has an extra key (e.g. 5K -> 2K + 3K). It is possible to increase the key count to 18K by combining Co-op and 9K mods. Note that this is possible on beatmaps, which are not osu!mania only.
• Random (osu!mania only) causes the note placement to change. It does not affect the note timeline.

Experimental

These mods do not appear on the "Stable" build and are not recommended for general use. The following mod names are placeholder names and may change.

• Target Practice turns the hit circles into bulls-eyes and you will fail if you miss a hit circle. this mod is similar to the Sudden Death mod. The speed is determined by the BPM of the selected song.

Mods with opposite effects cannot be used at the same time (e.g. Hard Rock and Easy cannot be used simultaneously). If multiple mods are used together, the final score multiplier would be the result of the multipliers carried by each mod multiplied together (e.g. if a Hidden mod along with an Easy mod was used simultaneously, the final multiplier would be 0.50 x 1.06 = 0.53).

Beatmap Parameters

HP Drain Rate is the rate at which HP decreases, which is always constant except during breaks. Further HP is lost with misses. HP is recovered by getting a score value and spinning spinners. More HP is recovered with a Geki and Katu at the end of a combo.

Circle Size (osu!, Catch the Beat, osu!taiko only) determines the size of circles and sliders. The value ranges from 2 to 7, with the smaller numbers being large sizes (like needle gauges). The smaller circles make the map harder by requiring the player to be more precise. Most maps use sizes 3, 4 and 5. 6 is sometimes used and 7 is almost never used (it will be roughly the size of the cursor). 7 is likely to be seen when using the Hard Rock mod, while 2 is always seen with the Easy mod.

Key Count (osu!mania only) determines the xK count for the difficulty. The value range from 1 to 9 with the selected number signify the amount of xK to be used on the difficulty. Clicking on "Co-op mode" checkbox doubles the currently selected amount (from 5 onward), leading to 10K (5), 12K (6), 14K (7), 16K (8), and 18K (9).

Approach Rate is a number (from 0 to 10) that indicates how long the hit circles stay on the screen, from the moment they appear until the time that the approach circles zoom in on the hit circles. Higher approach rates mean that hit circles will be shown for a shorter period of time, giving players less time to react. Inversely, lower approach rates mean that the hit circles will be shown on the screen for a longer time, with the approach circles zooming in slowly. This gives players more time to react to each circle, but can result in an excessive number of circles on the screen if the AR is too low.

The length a circle remains on the screen (without mods) ranges from 1800ms at AR0, to 450ms at AR10. Four mods can alter approach rate timing when activated:

• Easy: Halves the AR value. (ex. AR10→AR5 ... AR2→AR1)
• Hard Rock: Multiplies the AR value by 1.4, up to a maximum of AR10. (ex. AR3→AR4.2 ... AR9→AR10)
• Double Time: The AR value doesn't change, but the 1.5x play speed causes circles to stay on screen 33% shorter.
• Half Time: The AR value doesn't change, but the 0.75x play speed causes circles to stay on screen 33% longer.

Note: While Half Time and Double Time does not change the actual AR value, the speed difference can lead to an apparent AR as low as −5 or as high as 11. In the chart on the right, these apparent values are given to allow easy comparison between approach speeds with and without mods. Actual AR, however, is always a number from 0 to 10. Note that AR levels scale by 120ms below AR5, and 150ms above AR5.

Overall Difficulty is a number (from 0 to 10) that indicates how difficult it is to achieve high accuracy. Since accuracy is important for gaining HP, overall difficulty indirectly influences how hard it is to pass a map. Higher overall difficulties mean a smaller window of time in which one must hit a circle, both in general and terms of getting a 300. Spinners must also be spun more in order to fill up the gauge in time. Note that in some cases, raising the OD can make previously possible spinners impossible.

Approximate Difficulty Rating also known as "Stars" in Edit's song selection is a summary of all of the settings chosen on this page. More stars mean harder maps and more score. This is not the final star ranking of the song; it is an approximation based primarily on the composition of a map's composition of elements, although the difficulty settings chosen by the mapper plays a role in its difficulty as well.

At OD0, one can hit a 300 at less than 79.5ms away from exactly-on-time. On the other end of the scale, OD10 requires being less than 19.5ms away for a 300. Four mods can alter overall difficulty timing when activated:

• Easy: Halves the OD value.
• Hard Rock: Multiplies the OD value by 1.4, up to a maximum of OD10.
• Double Time: The OD value doesn't change, but the 1.5x play speed causes hit windows to be 33% shorter.
• Half Time: The OD value doesn't change, but the 0.75x play speed causes hit windows to be 33% longer.

While Half Time and Double Time do not change the actual OD value, the speed's effect on hit windows will make circles seem to have a lower or higher apparent OD, respectively. In the chart below, apparent OD values are provided to allow comparison between timings with and without these mods. Note that these apparent OD values only apply to 300s on circles. Windows for 100s, 50s, and sliders (which use the 50 hit window) scale more harshly with Double Time than this apparent OD suggests, and more leniently with Half Time. Again, outside of NoMod/HR/EZ (on the left side), the OD values below are only for comparison: the actual OD value is always a number from 0 to 10.

The osu! timing system does not allow a hit circle to be hit until the previous one has been hit or its time frame has been exceeded (resulting in a miss). With a low OD, the time frame of one circle may overlap with the next. Thus, one could hit the second note with perfect timing (after failing to hit the first note) and end up completely missing both because the time frame of the first note has not been exceeded yet.

Performance Points are a ranking metric that tracks how good a player is. Performance Points are heavily based on the map difficulty which is determined by a unique algorithm in every gamemode. Based on this difficulty alone each of the scores is rated and assigned a pp value.

Other Game Modes

osu! features three special game modes that are accessible in the mode selection of the play menu: osu!taiko, Catch the Beat, and osu!mania. These game modes allow a different style of gameplay from the standard play mode. These modes have separate leaderboards from the standard mode.

The osu!taiko mode is based on Taiko no Tatsujin, another rhythm game which involves hitting drums to the beat of a music piece. osu!taiko mode does not require the use of the cursor except for browsing the beatmap list and the pause menu. Instead, only clicking is required, which can be done with either a keyboard or a mouse. However, the osu! community has found various ways of supporting a Tatakon or DrumCon controller intended for Taiko no Tatsujin. Usually, an external script is used to map the controller input to keys on the keyboard. A PlayStation to USB Controller bridge is required to adapt the controller for a computer.

When playing the osu!taiko mode, red and blue beats, as well as long yellow drumrolls (with an appearance similar to a slider) will scroll across the screen – the player gets more points for the more hits they can achieve. The red beats are referred to as "Don" and the blue beats "Katsu". The red beats represent the Taiko (drum) center and the blue beats represent the rim. Spinners are also present in Taiko mode. Towards the left of the screen is a stationary circle. A player must hit the key(s) corresponding to each colored beat when a beat passes under this circle.

Catch the Beat puts the player in control of a character (named Yuzu) holding a plate above their head, with the objective of catching fruits falling from the top of the screen. Regular beats on a map are converted simply to fruit falling straight down. Sliders have one fruit at each end of the slider and a trail of juice drops leading between the ends. Large juice drops are the equivalent of hit circles, while small drops add extra points to the score and affect accuracy. Spinners become fruit falling en masse from the top of the screen; the player does not need to catch all of the fruit, although catching more fruit will earn them more points.

File:Osu!mania.jpg

Screenshot of osu!mania.

osu!mania is a mode similar to Beatmania IIDX and DJMax where players need to press keys bound to several columns according to the music. As the music plays, notes are falling from the top of the screen in several columns whose number depends on the map. As a note reaches the bottom row of some column, the player is expected to press the key bound to that column to clear the note, similar to playing guitar or bass in Rock Band or Guitar Hero.

Beatmaps

The game uses player designed "beatmaps", which are the files containing the actual gameplay data. These are created using an in-game editor, allowing the user to pick any song they like and produce beats for it. Beatmaps for specific songs can then be shared through an in-game uploader directly linked to the main site. Players can then provide feedback for the beatmaps, referred to as a "mod", usually suggesting some means of improving its quality. After the author has modified the beatmap according to the tips it received and the Beatmap Nominators are content with its quality, they may nominate it for ranking. Beatmaps must then undergo a seven-day trial period in the "qualified" beatmaps section, after which they will be moved to the "ranked" beatmaps section. Qualified maps have a high chance of returning to pending if an issue is found by a member of the Quality Assurance Team, even if some have garnered massive popularity during the ranking process.

To compensate for popular maps that haven't been approved, approximately late October 2016, a new ranking category was created for experimental beatmaps, called a "loved" state, which has nearly identical characteristics to the qualified state, with the exception of a loved map being community-voted, made available permanently, and with an ability for the beatmap creator to reset the scoreboard. Statistics for each ranked beatmap are maintained on the osu! website. Scores for each ranked beatmap are totaled to determine a player's ranked score, which determines a player's score ranking. Performance points are also given based on how well the player has beaten a beatmap, albeit not from qualified or loved maps.

As of February 20, 2018, over 400,000 beatmaps have been submitted, out of which over 15,000 have attained ranked status. The number of ranked maps gradually increase as the Beatmap Nominators rank submitted maps.

Multiplayer

On June 3, 2008, multiplayer was added to the public release (b335). Multiplayer consists of a central lobby displaying available rooms, and current online players. Rooms are created with the "New Game" button. A game begins when all players in the room are labeled as "Ready" and the host clicks start, or enough players are "Ready" that the host has the option to "Force Start". The Multiplayer game is made up of the normal components as a Single Player osu! game, but with the in-game scoreboard displaying the current rankings of the players in the room. All play modes (including osu!taiko, Catch the Beat and osu!mania) are available in multiplayer mode, as well as a variety of scoring rules, such as osu! Standard Score, where the highest score wins, or osu! Standard Accuracy where hitting the notes perfectly seizes the top spot. Players are also able to play tag co-op where the room works as a team to complete the song as each player is given certain beat clusters to hit, 1 player at a time. As of release b593a, Tag Team mode has been introduced where players are sided on two teams (Red and Blue) and work as one to win.

osu!world cup

Abbreviated as OWC, 'world cup' events are held yearly for each gamemode, named 'osu!world cup', 'taiko world cup', 'mania!world cup' and 'catch!world cup'. Teams from participating countries compete in a tournament bracket. They start with a group stage, followed with double elimination brackets. Stages are typically played one per weekend. The top three teams receive osu! merchandise, prize money, and a special badge on their profile page.

Non-PC platforms

As of November 2008, an iPhone/iPod Touch osu! port was announced and was released to the general public on January 2009 via Cydia repositories.

An official App Store version of osu! entitled osu!stream was released on August 1, 2011. osu!stream does not allow for user made beatmaps to be played, instead allowing only a select number of songs that are purchasable from an in-game store.

There is also an outdated port of osu! that has been released to Android known as osu!droid. This port was originally made by a member of the osu! community known as Pesets, and received negative reviews due to crashes. It has since been replaced by 3rd party ports such as opsu! or an unofficial patch for osu!droid.

At the Malaysia Comic Fiesta 2013 in Kuala Lumpur, peppy released a new peripheral, named the osu!tablet.

A version of osu! for Windows Phone 7 and 8 devices called osu!WP has also been released.

At various events peppy has shown off osu!arcade, a version of osu!stream that you would be able to play in arcades. It's not available to the public yet and appears to not have been for a few years.

osu!stream

An official version in the Apple App Store was added for the iPhone/iPod Touch called osu!stream. This version of the game does not include custom beatmaps; instead it has both free and paid beatmaps available for download from the in-game store.

On January 3, 2014, osu!stream was removed from the iOS App Store for copyright reasons. However, it was re-added to the iOS App Store on January 28 in the same year. Since the copyright infringement letters, beatmaps with links to Beatmania IIDX or Skrillex have been removed, although they can be found through external sources.

osu!stream has three gameplay modes:

• Easy: Slow beats, and it is impossible to fail.
• Stream: This mode is unique to osu!stream. This mode causes the gameplay to switch between "streams", or different difficulties in a single game based on the player's performance.
• Expert: Can only be unlocked if the player has achieved the ranking of "A" or better in stream mode. In this mode, gameplay is difficult with beats appearing faster, more stacking beats, more connected beats and faster drain of the health bar.

osu!supporter

osu! offers perks to players who contribute $4 or more. Supporters can download beatmaps directly on the osu! client through a program inside the client, named "osu!direct", and can automatically download from spectator or multiplayer matches as well as several other perks, including extra beatmap submissions, and the ability to change their in-game username once at no extra cost. After that, it costs $8 to change in-game username further

Reception

Jeuxvideo.com reviewed osu! favorably with 18/20 points in 2015.

osu!lazer

An under-the-hood and visual complete redesign of the game, named osu!lazer, was announced on May 22, 2015 by the developers.

The project includes a major overhaul of the graphical user interface as well as a ground-up rewrite and redesign of the home page.

On April 5, 2016, Lazer was announced, a completely new open-source software framework that osu!next will be developed on.

See also

• Beatmania IIDX
• Frets on Fire
• StepMania
• Osu! Tatakae! Ouendan

External links

• osu! official website
• Official wiki