Letters within letters! Type an uppercase letter followed by a lowercase letter to nest them. Type a period for an inner square, and > for an outer square.
This was an experiment from several years ago that I found half-finished while looking for potential CounterComp entries. I added missing letters and quite dramatically improved the existing ones. It's not perfect, and some combinations don't work so well (I'm particularly unhappy with capital I), but I think it turned out pretty well nonetheless.
Beware: for some reason, the downloaded font is huge-about 6 times the height of most other fonts-which makes it look horrible in e.g. MS Word, due to the pixel optimization at "small" sizes. I'm not sure what causes this, and consequentially, I don't know how to fix it.
Grulla's letters –built on a 2x3 square grid– have (tri)angular counters & square terminals. Counterspace=letterspace, letter /f/ is kerned onto "rounded" letters (fc,fd,fe,fo,fs). Diacritics support spanish (hello from Argentina!)