Juste before the smartphone explosion (~2008), I was working on a virtual machine for Windows Mobile, Symbian, Android 1.0, and basically every feature-phone of the time.

The VM (coded on good ol' C) would interpret a bunch of HTML, JS, CSS files (more or less like a browser) to run some tiny widgets above the phone's UI, basically allowing us to make multi-platform, custom UIs for low-end phones.

Everything was coded from scratch (except the JS engine which was a fork of SpiderMonkey), the VM could run multiple instances of itself, took around ~2MB of RAM to run (the exe contained everything in 1MB).

Oh, and we were a team of 3 beginner developers.

Fun times, no sleep times ❤️

EDIT: wow, the website is still alive O_o http://viamobility.com/