Learn more languages. I love deriving influence from all languages. In particular, I'm interested in Ruby,
Rust, Smalltalk, ReasonML, and Elixir.
Write a driver using the Linux framebuffer API. Although I never want to
specialize in operating systems, learning about them is fascinating and
helps me write better code at all levels of abstraction.
Implement TCP from scratch in C (bonus for x86 Assembly). We send a lot of data over the network
so I want to zoom in on how it's done.
Write my own kernel with some basic threading (RTOS style)?
Reduce the overhead of declarative web primitives (React style API close to the metal).