I'm interested in making a sandwich case for a keyboard with a single key. Although it seems it can handle a 2-key board fine, it doesn't work for a 1-key board.

The one key input:

[""]

with the following configuration:

results in the following weirdness:
.

But when there are even just two keys, i.e. ["",""], with the same configuration, it results in the perfectly well-formed:

I'm sympathetic to whoever programmed this--this is one of the few situations where somebody (me) actually wants an edge case!