Osteoarthiritis has claimed my thumbs. This keyboard firmware is hopelessly idiosyncratic, but it works for me. This layout is designed to allow typing without any use of the thumbs. Things like space, enter, backspace, and delete are all combos. There are lots of combos. Almost any symbol you need can be obtained with a combo. Mods follow home-row-mods logic, but other than shift, none are on the home row. Most mods are on the pinky column. Why? Because it keeps them away from the action zone where all the combos are.