Keynav is good but warpd [1] offers all of keynav's features and more (and on Windows, an equivalent of warpd is mousemaster [2]). They not only implement dichotomic splitting but the hint grid too. And they're both FOSS software as well.

[1] https://github.com/rvaiya/warpd

[2] https://github.com/petoncle/mousemaster

I don't get the last part where you repeatedly have smaller and smaller rectangles, can you expand on that? How are the rectangles defined? I pressed H, I'm at the center of the screen. Now what?

I assume something like this https://github.com/rvaiya/warpd/?tab=readme-ov-file#grid-mod...

Ok so just a warpd/keynav style grid mode then? I thought OP was describing a novel concept based on the idea that initially the whole keyboard would represent the entire screen.

Yeah, "Grid Mode" sounds similar. But instead of only 4 zones it would just roughly map the keyboard to dozens of invisible zones based on the position of the keys on the keyboard. So it would mostly be by feel. I have no idea if this would be better or worse than "Grid Mode" but it would be interesting to try it.

mousemaster is a warpd-like, opensource, for Windows: https://github.com/petoncle/mousemaster

On Windows, there https://github.com/petoncle/mousemaster which took inspiration from warpd.