"The "butterfly keyboard" which delivered a qwerty experience on a constrained keypad using rocker keys was conceived by Björn Ahlberg who is credited on the patent for this design."
via https://www.mobilephonemuseum.com/phone-detail/sony-ericsson-m600
If you're gonna constrain yourself to this kinda space you may as well go back to the numberpad + t9 predictive text
honestly we should go back to t9 on a lot of things because no way am I fucking typing out a message on a qwerty keyboard with a controller
nothing solved typing with a controller more elegantly than the psp did back in 2005

