Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics

Why is there no .crt file for download?

The game was developed for the GMod2 cartridge format and as such there's currently no way to run these files on the Ultimate. You would need to contact the makers of the Ultimate and ask for GMod support.

Explains a lot. Let’s hope Gideon’s Logic will add support for it then.