I love this! Happy to see I'm not the only crazy out there trying to port modern renderers to the Spectrum :D I've been meaning to experiment with assembly, but haven't gotten to that yet. This has some good ideas I'd love to play with.

Heh, I did a similar thing a couple of years ago when dogfooding my '8-bit homecomputer IDE' for VSCode (https://marketplace.visualstudio.com/items?itemName=floooh.v...).

I've come to the conclusion that it wasn't coding on assembly level that made development in the 80s slow, but old vs modern tooling. E.g with good tools coding in assembly isn't all that much less productive than coding in a higher level language (unless you're just glueing together 3rd-party packages of course).

With a good macro assembler you're already much closer to a highlevel language like C than to machine code, and with a quick 'edit-compile-debug' loop using an emulator for running the debugee that allows to inspect the entire machine state (and not just the CPU state) you get pretty much the same productivity as working in a "proper" high level programming language, just with a slightly different approach to abstractions (in assembly code, subroutine calls and data layout are your abstraction tools, not the type system of a highlevel language).

Here's the demo I built (no sound, because I suck at sound):

Source: https://github.com/floooh/kcide-sample-kc854 (note: if you're logged in to Github you can just press '.' (dot) to start into the web-version of VSCode which after a little while will ask to install recommended extensions).

Running in emulator via WASM: https://floooh.github.io/kcide-sample/kc854.html?file=demo.k...