Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics

Inside the MacOS folder there is a file with the same name of the package (Alisa Demo (Mac) v1.33b). This is the file to add "x" attribute. Might be necessary to add "sudo" in the command line he show in the video (sudo chmod +x ...), so the Terminal will ask for your user password to perform the change.