Yep, it was the .app file but for some reason it won't open. The symbol for the game pops up a split second when I try to launch the app, but it also disappears just as swiftly without anything else showing up on screen. I did however notice that I got a steam key with my purchase so I'm going to try launch it through that and see if I'll have any better luck there :)
Viewing post in All Idleness and Ephemera comments
The Steam version of Idleness is 100% identical to the Itchio version, so if the Itchio version doesn't work I'm doubtful that the Steam version would. I can try and take another look at it later, but as I don't have a Mac it will be more or less impossible for me to troubleshoot any issues on my own.