Wait... Why Did It Say:
“Hell_Cat” cannot be opened because the developer cannot be verified.
When I Opened Hell Cat
Are you on Mac? Must be some Apple shenanigans I can't really debug... You can always download the .P8 file and load it up in PICO-8, either via the standalone executable or the free Education edition online (This game was made for a fairly old P8 version so maybe it wont work on recent versions tho).