Silhouette Mirage is one of Treasure's more divisive titles, but it's still an amazing 2D action experience – and it seems the game's Japanese 'trial' version has been hiding a secret.
According to @memory_fallen, the Sega Saturn Silhouette Mirage: Trial Version disc – which, like the game itself, was exclusive to Japan – contains a late prototype build of the entire game.
Normally, the demo ends after level two, but a late pre-release version of the game – dated 1997-07-16, a few weeks before the final version (1997-07-30) – is on the disc.
"The patch works by giving the demo a bit of a brain transplant from the final version," says memory_fallen. "The trial disc has all of the stage files on it, but doesn't know how to access them. With the code from the final, the only thing that doesn't seem to work is the save game functionality."
You can read more about how the patch works here, and the patch itself can be downloaded here. You can either run this via emulation or play the patched demo onto your Saturn via a CDR or ODE.
Silhouette Mirage was Treasure's second Saturn release, following Guardian Heroes. It would later be ported to the PlayStation, with that version getting a Western release via Working Designs.