If you've never heard of the Taito X-55, don't feel bad – most people haven't, to be fair. This 1995 home karaoke system was only sold in Japan, where it shifted around 200,000 units – hardly blockbuster territory. It allowed players to download games over a wired internet connection.
Despite its karaoke leanings, the X-55 also ran 'normal' games, one of which is 1997's Crescent Tale, a single-screen platform title which clearly borrows elements from Taito stablemates Bubble Bobble and Don Doko Don (thanks, gosokkyu).
Because games were downloaded to the machine rather than sold physically (a concept that was first pitched via the unreleased Taito Wowow), it was assumed that this title had been lost in the mists of time – but its original planner "FUINARLE" has discovered not only the original design documents for the game, but a backup copy which runs on original hardware:
So, the game is 'preserved' at least, but will it ever be made available to the wider public? That remains to be seen, but it's fascinating to see a game that was considered to be lost forever suddenly popping up online.