What it is
iOS rhythm game with 11 tracks, distinct mechanics per track, "soft girl era" sonic and visual aesthetic. Bundles the Beat Map Editor (authoring), Soft Girl Era Mastering pipeline (audio), and a custom playable game engine.
Functions as the consumer-facing, non-research-coded surface of the suite: the playable instrument.
Where it sits
SOFT GIRL ERA (IOS) is catalogued under Hardware & Concepts in the instrument registry. Instruments in this group share a concern and are frequently composed rather than used alone; the related entries below are the nearest ones.
This is a registry entry: a real instrument, documented here, without a public endpoint a stranger can open. Pages carrying source excerpts and measured results are marked as such in the catalog. If you want detail on this one specifically, ask about it directly.