@nixCraft
this gem. (english version: https://www.acornelectron.co.uk/ugs/electron/acorn_computers/ug-english/contents_eng.html / https://www.retro-kit.co.uk/user/custom/Acorn/8bit/Electron/manuals/Acorn_ElectronUG.pdf)
Sophie Wilson's BBC Basic was soo cool. You had procedures, functions, inline assembler...
think i also had some other book, it showed how to do 3d graphics per multiplication of matrices etc. anyone remember which that might have been? maybe "The Acorn Guide to the Electron"?