Ask HN: Examples of nice open source software that are written as single file?

Are there examples nice open source software or tools that are written as single file?

These could be big or small projects but it needs to fit in a single file of source code.

Like if it is a C project, then it should be a single .c file. Or if it is Rust project then only single .rs file.

Why do I care about this? Just pure curiosity. I hope to discover some interesting projects in the answers.