A recreation of Vim’s core editing experience with nothing beneath it: the whole editor is x86 assembly and boots straight on the machine through GRUB, with no operating system underneath. Everything a programmer takes for granted (reading a keystroke, drawing a character, remembering what changed) had to be built from the hardware up.
The editor implements the essence of Vim: modal editing with normal, visual, and replace modes, operators and movement commands with repetition counts, block selection, find and replace, text search, and undo.
In practice that means direct keyboard input handling, video memory manipulation for rendering, and text buffer management with undo history, all in assembly, split into clean modules for booting, input, display, and each editing mode.
Built as a systems programming project, the kind of exercise that changes for good how you read the phrase “high-level language.”