boot
A 512-byte integer BASIC interpreter is surely a feat by Oscar Toledo, also known as nanochess on GitHub, where bootBASIC's source code resides. As of June 2023, this project from 2019 seemed to be alive, in spite of its Assembly code being apparently untouched for 3 years already.
According to the project's README file, the NASM-assembled code runs on the Intel 8088-based original IBM PC. There are ports for 32-bit and 64-bit Macintoshes as well.