For those who may not be familiar, iidx and BMS (Beatmania IIDX and Bemani Sound) are popular Japanese music games developed by Konami. The games feature a wide range of music tracks, many of which are created by renowned artists and producers.

The term "mirrors" refers to a specific type of song pack or "sub-pack" that contains remastered or re-created versions of classic tracks from older Bemani games, often with updated graphics and gameplay features.

A very specific and niche topic!

"Repack" likely refers to a fan-made or third-party compilation of these mirrored song packs, possibly with additional features or modifications.