- April Fools' Day 2019
- Tap several times on the "Like" (heart) icon of any song except Ignotus.
- April Fools' Day 2020
- Tap several times on the "Like" (heart) icon of Red and Blue.
- The 2 arc notes with 900° rotation may be successfully cleared by:
- Rotating the device (easiest and least risky option for most players).
- Physically moving around the device.
- After roughly every 360° rotation, releasing one arc note then quickly moving the released finger around and back onto it.
- This song is a remix of several songs in Arcaea, and is only available on April Fools' Day since 2019. The songs are:
- April Fools' songs have several idiosyncrasies:
- Future only: no Past and Present difficulties.
- Undefined difficulty level: the Future chart difficulty is just displayed as "?".
- Undefined chart constant: playing this song has no effect on Potential.
- Camera feature: notes can be outside the usual input boundaries.
- This song has several peculiarities of its own:
- A 3rd type of arc note is introduced, which is green in color.
- A total of 5 fingers are needed for this song; more fingers than any other song.
- There is a section where 2 arc notes in a double helix have a rotation greater than 360° (900°).
- When using a partner with the MIRROR skill, instead of the usual change of colours for arc notes, they change in accordance with this table:
- When using Colourblind arcs, both red and green arcs appear the same shade of yellow
- Although the heart icon was removed after April Fool's Day, it was still visible (although not accessible) due to an oversight in World Mode on the random song for Random Song Tiles. This was also patched in version 2.0.3.
- The name fn(ArcaeaSoundTeam) is both a reference to mathematical/programming functions and an allusion to the artists that worked on it, Frums and Nitro.
- This song’s Future chart has the third highest amount of notes (1508). For other charts with high note counts, see Misc Trivia.
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