Flow is a mapping concept that describes natural and intuitive movement patterns of a player's cursor during gameplay. Flow, or the lack thereof, is related to the osu! game mode due to its two-dimensional playfield. By utilising the vast variety of patterns and slider shapes possible in osu! beatmaps, mappers are able to direct a player's cursor around the playfield in various ways, yielding different effects on the gameplay experience.
Flow is considered a subjective and often opinionated matter due to how different mappers and players design or perceive movement. Some aspects of flow may impact gameplay to different degrees depending on the player's input device, such as graphics tablet or mouse, or the player's acquired skill or experience.
The opposite of flow is called antiflow, which conversely involves unintuitive or unnatural movement patterns.
While movement preferences vary from one person to another, there are a few ideas that give the feeling and impression of flow on a majority of patterns or whole beatmaps.
Series of hit objects that require smooth movement, without sharp, abrupt turns, or fast changes of pace, can be considered comfortable to play. In such patterns, the player's cursor may follow a smooth curve throughout. These curves are usually characterised by circular or semicircular segments (so-called oval or circular flow) going either clockwise or anticlockwise. Beatmaps often switch the direction of the circular flow at regular intervals,1 where the transitions are often accompanied by "neutral" patterns to ease the transition to the next pattern.
Linear movement may also be considered another form of smooth flow, albeit less common, since it does not enforce any specific cursor trajectory type.
Another form of natural movement is repetition. Patterns with similar repeated movements that only differ slightly, such as back-and-forth jumps or a series of slider pairs, are comfortable to play due to subsequent movements following already familiar paths, making them easy to predict. Repeated patterns may become more and more comfortable throughout a map for the same reason.
To further make a beatmap look and feel more natural, mappers may use sliders with different shapes that reinforce suggested direction of movement. Since slider bodies do not need to be followed perfectly, because the cursor only needs to reach the slider ticks, they may be adjusted and bent in lots of ways without affecting the movement required to clear them. This allows slider shapes to complement an existing movement trajectory, or help the player pick up a new movement trajectory.
In beatmaps, different types of flow can be used to express different aspects of the music.
For example, smooth flow can be contrasted with unnatural movement to demonstrate differences in a song's intensity during key moments. On the other hand, repetition is regularly used to show a repeated part of a song.
Due to the subjectivity of flow and the amount of possible cursor movement patterns, there is no clear consensus regarding how flow should best be used in beatmapping.
For players using a mouse, circular movement applied in the same direction for too long is viewed as both too repetitive and uncomfortable due to mouse drift. ↑