The format would have been an RPG Maker horror game ala Witch’s House or Mad Father, specifically inspired by Mario and the Music Box, with a ton of ways to die (complete with death CGs) and different endings depending on how many foals you found. It was too ambitious for me and so fell through, which is why I instead made it a written story, but you can find a bunch of the concept art here. (Warning; the concept art contains spoilers for several later story events!)