@vertigo #picolisp is pretty !forth-like in a sense. Its a very small kernel, it bridges well with machine code and most of it is written in picolisp. But the kernel is in assembler and quite tied to the hardware. pico for x86-64 an x86 even have different features. I guess that makes it both easy and hard to port. Tiny kernel, but you need to rewrite it all each time.