[[caption-width-right:350:''~ ♫ [[https://www.youtube.com/watch?v=gbNm4bqoXNI Click the circles...]] [[RhythmGame to the beat!]] ♫ ~'']]

-> ''Welcome to osu!''

''osu!'' is a {{freeware|Game}} {{rhythm game}} made by Dean "peppy" Herbert, based on the gameplay of the ''[[VideoGame/OsuTatakaeOuendan Ouendan]]'' and ''VideoGame/EliteBeatAgents'' series of games for the [[UsefulNotes/NintendoDS DS]].

Game levels, called beatmaps, are created and submitted by users via a LevelEditor. These can later be refined through community modding if the creator requests it and gets [[OfficialFanSubmittedContent ultimately approved]] by members of the Quality Assurance Team and Beatmap Nomination Group.

Ranked beatmaps give Performance Points (or [[FunWithAcronyms pp]], for short) after being beat, [[DoubleEntendre giving more pp]] the better you did in the map, and they also get a scoreboard featuring the best scores done in it. The beatmaps also give experience points based on how you much you scored in them, [[CosmeticAward but the levels do nothing and are ultimately cosmetic]].

Besides the Ouendan/EBA gameplay, osu! includes three additional game modes: one based on the ''[[VideoGame/TaikoDrumMaster Taiko no Tatsujin]]'' series, one based around the gameplay of ''[[VideoGame/{{beatmania}} beatmania IIDX]] [=/=] O2jam'' and another revolving around catching fruit.

Apart from Solo mode, players can [[CompetitiveMultiplayer compete]] in all four modes in online multiplayer matches in rooms which can contain up to sixteen players, in single or team battles, in order to get the highest score, accuracy or combo possible, [[CoopMultiplayer or play beatmaps together by taking turns between combos]], depending on the room settings. In osu!mania, two players can play locally using the same keyboard.

Its website can be found [[http://osu.ppy.sh/ here]] and the game can be downloaded [[http://osu.ppy.sh/p/download here.]]

!!This game provides examples of:
* AllLowercaseLetters: The game is called ''osu!'', and most of the community [[BerserkButton doesn't like it]] when people call it "Osu!" or "OSU". [[https://www.reddit.com/r/osugame/comments/4s7u0z/what_is_the_most_satisfying_thing_about_osu_for/d57mlzw Not even the main developer likes it.]]
* {{Anime Theme Song}}s: Around 1/3 of all the ranked maps are these.
* AprilFoolsDay: The jokes each year revolve around changes in the game's genre ("Touhosu", a VideoGame/{{Touhou}}/osu! hybrid), gameplay ("osu!core", where the songs in every beatmap had their pitch and speed increased), staff (unexpected demotions or promotions), and beatmaps (pretending to approve and praise an extremely poorly made beatmap).
** Also, some of those jokes have ascended. osu!core became a permanent available mod called Nightcore, and Touhosu! has been confirmed as in development by peppy.
* CallAHitPointASmeerp: The currency of this game is called "kudosu", and is earned through modding unranked maps.
* CrossOver: The beatmap for Music/{{Queen}}'s [[http://osu.ppy.sh/s/5381 Don't Stop Me Now]] is based on the plot of a FanFic which combines [[Franchise/AceAttorney Phoenix Wright]] with ''VideoGame/EliteBeatAgents''. It's as awesome as it sounds.
* {{Determinator}}: A player can become this if they're trying to pass, get an FC (Full Combo), or enter the Top 50 on a beatmap, especially if the beatmap is pretty difficult. If they lose a rank in the top 50, don't expect them to quit playing for hours until they beat the player who beat their score.
* ExcitedShowTitle
* FakeDifficulty:
** Is HEAVILY discouraged nowadays, and maps with it have a very low chance of being ranked. Using tricks like low (or high) Approach Rate, high HP drain, etc., are no longer acceptable in the Ranked Beatmaps section. In addition, some very specific mapping techniques are not allowed to be ranked due to being very confusing and frustrating for players. A list of these can be found [[https://osu.ppy.sh/wiki/Unrankable_Techniques here]]
** There was a time when maps could be [[https://osu.ppy.sh/s/132 impossible to S-rank,]] [[UnwinnableByDesign even by Auto.]]
** Or have FAKE SPINNERS in the [[https://osu.ppy.sh/s/3959 storyboard.]]
** Playing for score? Aside from the combo multipliers practically encouraging restarting over one mistake, modifiers add to your score, most notoriously the modifier that increases the song's speed by 50% to give a 12% score boost. So to get high-ranking scores you have to alter the song.
* FunWithAcronyms: GMT (Global Moderator Team), QAT (Quality Assurance Team).
** Also some, teams that don't exist anymore, like MAT (Modding Assistance Team), BAT (Beatmap Appreciation Team).
* GameWithinAGame: Taiko, Catch The Beat, and osu!mania modes.
* GradeInflation: As in Ouendan and EBA, S comes after A, but a perfect performance in osu! earns the player an SS rank. An SS achieved under the Hidden and/or Flashlight mods has a separate sprite (alternate colouration in the official skin) and commonly referred to as "SSH".
* IdiosyncraticDifficultyLevels: Beatmappers can name the difficulties of a beatmap set into whatever they like. However, NonIndicativeDifficulty names on a beatmap set's lower difficulties render it unrankable.
* HarderThanHard: Many beatmaps have an Insane difficulty, and some even have a difficulty above Insane (officially named "Expert").
** "Oni" and "Inner Oni" respectively for Taiko beatmaps.
* InterfaceScrew: The Hidden and Flashlight mods.
* LevelEditor
* {{Mascot}}: [[https://osu.ppy.sh/wiki/Mascots#Pippi Pippi.]]
** [[https://osu.ppy.sh/wiki/Mascots#Yuzu Yuzu]] for osu!catch.
** [[https://osu.ppy.sh/news/143103453693 Maria]] for osu!mania.
** [[https://assets.ppy.sh/media/mocha/mocha-header.jpg Mocha]] for osu!taiko.
* MarathonLevel: There are a handful of "marathon" beatmaps, commonly ranging between 10-15 minutes in length, with some even longer:
** [[http://osu.ppy.sh/s/972 paraparaMAX I]], at 36:17.
** Music/WithinTemptation's entire album ''[[http://osu.ppy.sh/s/29157 The Unforgiving]]'' in one beatmap, the current record holder at 52:57.
** In addition, there are several unranked maps that pass the 100 minutes mark, also some of them are over Insanely difficult!
* NintendoHard: Thought ''VideoGame/EliteBeatAgents'' and ''VideoGame/OsuTatakaeOuendan'' were hard? You haven't seen anything yet. The hardest songs from Ouendan/EBA are approximately 3.5 stars on the revised star rating scale released in mid-2014, and these games are already Nintendo Hard on their own. The hardest songs on Osu takes this UpToEleven, with revised star rating exceeding 7 stars, such as [[http://osu.ppy.sh/s/24313 "Can't Defeat Airman"]]. Such crazy streams and jumps do not exist in the original Ouendan/EBA games.
** A common joke between pro players (rank 1000 or less) is saying they have problems passing "Can't Defeat Airman", there are a few beatmaps where almost all players have to struggle, such as "xi - FREEDOM [=DiVE=] (FOUR DIMENSIONS)", or "IOSYS - Utage wa Eien ni ~SHD~ ([=TAG4=])". (Though that one is meant to be played by four players simultaneously.)
** Prior to the mid-2014 update of difficulty calculation system, original star rating scale could not keep up with the escalating difficulty of the newer beatmaps with topped off at 5 stars.
*** There are the few maps that completely break the old star rating system, such as xi - FREEDOM [=DiVE=], where the hardest difficulty is rated at around 2.5 stars, which is the average Easy difficulty rating, and the other, also insane+ difficulty is rated at 4.5, which is a typical Hard difficulty. Certain maps with high difficulty settings go ABOVE the 5.00 limit (although not by much).
*** Adding on, there are several joke maps with star ratings into the negative and beyond, even reaching up to -infinity/5 in some weird special cases.
** For osu!mania 4-key, there are some maps that, while they would only be maybe a 6 star map in osu!mania, they could go up to 20-footers in Stepmania (like That Was Too Slow [4K MX] or miracle 5ympho X [Black Another]). An 8.5-star map might be around a 26-footer ''or harder'', something like Kinetic or UKF Dubstep VIP in Stepmania.
* NonIndicativeName:
** The Double Time modifier multiplies the speed of the song by 1.5x.
** The Half Time modifier multiplies the speed of the song by 0.75x.
* OneHitPointWonder: The following modifiers do not increase score, and considered to be convenience modifiers for players who are going for a (perfect) full combo run to quickly restart the beatmap:
** In the Sudden Death mod, you fail the beatmap you're currently playing if you screw up once.
** With the "Perfect" mod, you lose instantly if your accuracy goes below 100% at any point.
* PinballScoring: In standard mode, the maximum possible score of very long beatmaps with huge note counts can grow to very large numbers. In one extreme example, the very long "[[https://osu.ppy.sh/s/29157 Within Temptation - The Unforgiving]] described in MarathonLevel above has 10-digit scores in the top four ranks (as of this edit). To get good scores in any given map, getting a full combo is crucial. Tournaments instead use a "score v2" system with a maximum 1,000,000 points and avert this trope.
* PowerCreep: To a certain extent. The players are getting better, of course, but there are also more and more maps that can be "farmed" to earn PP. At the end of 2014, the highest PP score was 558. At the end of 2015, it was 667. In the first month of 2016, there have already been five scores that have been higher than that.
* RageQuit: A common practice to avoid submitting and saving low accuracy scores, though that doesn't work anymore.
* RhythmGame
* ScoringPoints: There are two scoring systems: the "[=PointValue=] x ([[ScoreMultiplier combo]] + [=ConstantA=]) x ([=ConstantB)=]" system used in the source games, and the "pp" system (which gives a score according to how impressive the play was). There are also scoring systems that are exclusive for multiplayer matches, such as accuracy (percent-based system, which is the average accuracy for each note, being a 300 a 100%, a 100 a 33.33%, a 50 a 16.66% and a MISS a 0%), and Combo (the player with the biggest combo the moment when the map ends wins). In a multiplayer match, you can choose which system to use for ranking.
* SelfImposedChallenge: Using one or more of the difficulty increasing mods and/or going for SS (perfect) runs.
** Playing with a "blind" skin is this, which is a skin with an invisible hitcircle. Players who use these kind of skins may also play with the Hidden mod, which hides the approaching circle.
* StylisticSuck: [[http://osu.ppy.sh/s/23058 NotShinta's cover]] of Music/ImogenHeap's [[https://osu.ppy.sh/b/36067&m=0 Aha!]] is awful. Yet so very good. Notable for being the beatmap with the lowest user rating on the site.
** The Jarto series is based on this trope, having an... odd narrative told through Stylistic Suck storyboards.
** Spinsmith also has his series of bad song covers.
** [[https://osu.ppy.sh/s/21145 ztrout]] is like Aha?, except it came first.
* SuperDeformed: Miniature versions of [[{{Mascot}} Pippi]], [[VideoGame/OsuTatakaeOuendan Ryuuta]], and [[VideoGame/EliteBeatAgents J]] can be found on the homepage and Catch The Beat.
* UpToEleven: Somewhat literally. There are 4 values for every map (Approach Rate, Overall Difficulty, Circle Size, and HP Drain) that the creator of the map can set from 1 to 10. The Hard Rock mod increases all of those ratings by a set amount, always maxing it at 10. The Double Time mod is an exception to this rule because it actually speeds the whole game up by 1.5x rather than directly changing the variables, this causes the game to play an [=AR10=] map at 1.5x speed, making it play as if the map had [=AR11=], even though their max is 10 in the game's code. [[https://youtube.com/watch?v=_VrkG_CAI1E This]] is what an [=AR11 OD11=] map looks like.
** Taken up to '''12''' in Taiko mode.[[note]]Each OD notch in Taiko decreases the hit windows by 3ms. OD10 in Taiko is 19.5ms, 13ms when time modded.[[/note]]
-> ''See you next time...''