Works in at least Catalins but the developer link (above) is now dead. The link to the developer's website should be https://www.amie-chen.com/projects/ (although the Prezel link doesn't work).
Pretzel can still be found on the devr's GitHub page at https://github.com/amiechen/pretzel
There's no option to launch at login, so it has to be manually added to a user's login items, and as Weasel wrote the app icon is weird in anything but icon view, but it's a great free app.