An operating system that is just a trollface. Install this on a machine to surprise the next person to boot it.
On Ubuntu:
sudo apt install grub-pc-bin xorriso nasm
Then run make to compile an ISO with the operating system.
On a Mac, it's a huge pain to get this thing working. In the end, my solution is to use a Linux Live CD to install GRUB on the machine, and then replace the grub configuration file with a trollface.
Boot into an Ubuntu Live CD. Use fdisk to create a partition table and put one HFS+ partition. Use mkfs.hfs (installed via apt install hfsprogs). Then use the grub-install command to setup GRUB on the disk, and use hfs-bless to bless the boot.efi file. Finally, replace the grub.cfg file with the one stored in this repository.
You may encounter errors with grub-install. Sometimes, it's necessary to copy the contents of / to the Mac volume, and then to chroot into the Mac volume. Don't ask me why.