Good for you. The days when we where expected to right code without a computer ended quite some time ago. It takes a lot of strength, intellignence and maturity for the candidate to terminate the process and I respect that from both sides of the table.
you know, i quite liked the position, but i was always told that "interviews are two way streets". if that's how they interview their candidates... well, let's say i don't want to work with people that were hired with that process.
the good thing is that i interviewed and was hired about three weeks later -- and it was an even better position!
i asked if i could at least do on my editor of choice while screensharing -- "nope, too complicated".
i asked if i could do in pseudocode, nope "it must at least run".
i tried for 10min, said "thank you, but i don't think this is working for us -- we can probably stop here. thank you for your time [yadda yadda]".