I use keyboard with similar concept as this for more than 10 years. It uses a 3 by 3 key with additional column for control so like an old phone but swipe based. I like it because I can use 1 hand to write on phone. The application called MessageEase[0] before they go subscription based and now I use Thumb-Key[1].
Does anyone remember another HN post that has same topic(about personal project/blog/open source contribution) a few months ago? I wanted to save the link but forgot what it is. Can anyone share it if you remember? thank you in advance
[0] https://www.exideas.com/ME/ [1] https://github.com/dessalines/thumb-key