Ask HN: Tiny end to end hobby projects that turned big?

The most recent example I can recall is that of Photopea. It was created by one person as a uni student to solve a small problem. Now it is used by millions. The founder recently launched another project Vectorpea. It is a bunch of JS files that load in your browser and after than you can even work offline. Server costs are minimum. You can read the detailed interview here: https://www.failory.com/interview/photopea

What are some other examples of solo founders making end to end systems without any bloat and later making it big?

P.S.: Needn't be only software projects.