What are some one-person engineering marvels of recent times?

GIT - As I understand it: Linus got fed up with the licensing issues and non-technical disputes around BitKeeper and went off to solve the issue once and for all by building an open source replacement.

It's an amazing snapshot engine, that acts like it stores deltas.

Programming in the 1980s wasn't really awful, we were getting newer faster cheaper computers all the time... the only thing that really sucked was making source01.zip, source02.zip, etc on stacks of floppy disks to save our source code. (Hard drives crashed all the time back then)

GIT is like manna from heaven in comparison.

The Marble (Music) Machine: https://www.youtube.com/watch?v=IvUU8joBb1Q

I think bun was built by a solo dev