Sometimes when people press multiple buttons in the lift in my office building, I see a Braille letter. (The buttons are in a 4×4 grid.)
Yesterday and today, there was a >-shaped pattern that’s Braille "o" (at different positions; yesterday, my floor was the middle dot, this morning, the top dot).
And I noticed that as the “lower” dots progressively disappeared, that the corresponding Braille letters remained vowels! Interesting.
First, there was a ⠕ “o”, then a ⠑ “e”, and finally a ⠁ “a”.
It was a bit like discovering that you can build up a katakana letter stroke by stroke with each new stroke forming a new letter along the way (though you wouldn’t write it in that order): ノ “no” --> フ “fu” --> ワ “wa” --> ウ “u”.