- Bash, POSIX shell, and "venerable" Linux userspace - Debugging/Troubleshooting gnarly issues - J (https://www.jsoftware.com/#/) - Guix (https://guix.gnu.org/) - Metamath (http://us.metamath.org/) - Having a good time - Differential geometry and statistics - Physics (of pretty much anything!) - ELF, linking/loading, Linux kernel processes - Libreboot and Coreboot (in that order) - Deconstruction of direct experience