Thanks! I went so far with it that I was honestly questioning my own sanity.

The HAL has a virtualized CPU, and I spent more time than I’d care to admit precisely timing instructions on various period-accurate hardware (386SX, 486DX). I even tuned it to the point where programs that take advantage of it actually run faster on the 486 because of the built‑in math coprocessor.

> Writing directly to VRAM? WAIT for vsync?

All screen modes are supported including the ability to draw to hidden pages. It’s got a fully emulated VGA hardware layer and even a synthetic VGA beam clock, so you can do tricks like `WAIT &H3DA, 8, 8` for vertical retrace to minimize flicker.

> Call absolute for mouse usage?

Yup! Int 33h is fully supported, we basically use a virtual TSR driver which is pointed to by the interrupt vector table. I actually tested it with an old pixel art editor I made in the 90s!

PEEK/POKE and much of the BIOS are fully simulated, so you can use more advanced QuickBasic 4.5 features like calling interrupts (including silly stuff like rebooting the computer via int 19h).

There's a ton more (including a Hayes compatible modem plugged into COM1) as well.

I basically dug out a stack of my old PC books from the late ’80s and early ’90s, and they’ve been my bibles for the past several months (Undocumented DOS, The Programmer’s PC Sourcebook, etc.).

It’s about 99% done at this point. I’m hoping to do a Show HN in the next couple of weeks.