Ask HN: Technical side project ideas for full stack engineers?

Trying to get ideas for technical side projects to help me improve my depth of understanding on certain parts of the stack. Current rough ideas: * Write a react runtime * Write a js compiler * Write a node.js runtime

Curious if anyone else has any other ideas, or if there are any senior engineers out there that have done projects that really helped them in their career. (In either expected or unexpected ways.)