If you use keyCode instead of charCode I think you'll get the same result on every keyboard layout, but of course if you tell people to use C, it means the key

If you use keyCode instead of charCode I think you'll get the same result on every keyboard layout, but of course if you tell people to use C, it means the key where C is on a US keyboard, not really the key where a C is printed. I believe Dvorak users are conscious enough to understand that though.