A really (!) small keyboard design has been announced that will challenge your ideas of small. Details are
here.
No doubt, this will find its way into some new DIY calculator designs!
And just when I thought it was reading screens with worsening eyesight that would be the usability limitation....
On the bright side...
If my eyes are too bad to read the screen then it does not matter which keys I press.
No doubt this was inspired by the little [X] button on most website ads....
I'd rather use a swipe-style keyboard, which would probably be about as accurate as trying to use that tiny keyboard with my larger fingers.
An unexpected benefit of small buttons is that the area to hit with your finger is up to nearly twice the distance between buttons. Comparing this tact-switch keyboard with the nearby thread on a circular keyboard, where the buttons butt up against each other, I know which one I'd prefer.
There's a related design detail in low-travel laptop-style keyboards: the keys are usually bevelled, so the hit area can be larger than the key spacing.
(It does so happen that I have relatively small fingers.)
Link direct to this keyboard project:
https://hackaday.io/project/178204-the-s...t-keyboard
And to a video:
https://www.youtube.com/watch?v=V2ivH2PEoiA
which does show that the keyboard is really quite small...
Some ten years ago I was given a Blackberry as my Company phone which had a proper keyboard (instead of today's touchscreens) with even smaller keys. Initially I thought it would be impossible to use but it turned out to be quite practical.
This was my best phone ever as far as hardware
You could type fast on the keys and slide your finger over the keyboard like a touchpad to control a (mouse) pointer
But Blackberry didn't seem to be able to handle the software side. They would push out monthly updates and every month broke things, they were as bad as Microsoft.