The game features a simple piano controller placed just below the screen. As notes descend on the screen, the player must hit the corresponding portion of the controller in time with the notes. The player does not need to hit the exact key; as long as the key pressed is within the width of the note, it will count as a note hit.
Games in the seriesnote :
- Nostalgia (2017)
- Nostalgia FORTE (2017)
- Nostalgia Op. 2 (2018) — current version
Nostalgia provides examples of the following:
- Button Mashing: Trill notes require you to repeatedly hit keys within the width of the note until the note ends.
- Bribing Your Way to Victory: Expert charts can either be unlocked by getting A ranks on Hard charts, or paying some extra PASELI (which itself is bought with real cash) to play Forte mode, which has them available immediately.
- Call a Hit Point a "Smeerp": Hold notes are called tenuto notes, similar to how tenuto notes in real-world music parlance are meant to be held down.
- Color-Coded for Your Convenience: Notes are colored blue or red to indicate which hand is meant to hit the note (blue for left hand, red for right hand). That said, the game does not care nor can it tell which hand you hit notes with; the colors are simply a guideline.
- Fake Longevity: Want to play Expert charts? Get an A rank on the Hard chart first. Or, pay extra cash to play Forte mode, which has them available with no further requirement.
- Harder Than Hard: The chart difficulties are Normal, Hard, Expert, and Real.
- Have a Nice Death: Failing a song results in a "Finish..." screen (as opposed to "It's fantastic!" for a clear), in a tone that sounds like "well uh, you made it to the end of the track I guess."
- Required Spinoff Crossover: To absolutely nobody's surprise, "FLOWER" is part of the tracklist, this time as a piano arrange.
- Spiritual Successor: To Keyboardmania. Both games simulate the same instrument (piano and similar keyboard instruments), Nostalgia in particular has tracks that are explicitly billed as Keyboardmania crossovers, some of which have not appeared in any other game, and Nostalgia Op. 2 introduces a Harder Than Hard difficulty called "Real", a difficulty name that had not been used since Keyboardmania 3rd MIX. That said, Nostalgia is much easier to learn, due to notes corresponding to ranges of keys rather than requiring the exact key to be hit and eschewing a Life Meter in favor of a score-based pass/fail system.