I used twiddler 2 (I think). It was cheaply made chorded keyboard. I admit I did hold down the keys rather hard while learning to use it. Soon after I'd learned

I used twiddler 2 (I think). It was cheaply made chorded keyboard. I admit I did hold down the keys rather hard while learning to use it. Soon after I'd learned the patterns the keys started breaking. I took it apart to take a look, all the keys were connected by tiny bridges of plastic. When the plastic bridges broke the keys became loose and non-functional.