I want to play this except I don't know which file to play on
Are you using mac? There should be a launcher file in the game folder, but it looks like it's gone here. Please try using itch.io launcher to play the game, and if the problem persist, let us know.
Update (30-8-2021):
We got a report that the build for mac OS is not working. Try launching the game by using itch.io launcher (similar way to using steam launcher to launch games). https://itch.io/app The game should be working just fine, but please let us know if the problem persist after you did it.