Hello - I'm trying to get my students to work on something creative. Squiffy is the exact thing I've been looking for. Is there any way to get special characters like ż ź and so on in squiffy ?

Actually, it's quite easy. Simply type them into a word doc and then cut&paste them into the editor. You should see them there, and you'll also see them when you run the game.

I tested this by cutting and pasting your characters into my own game and they came through fine. Hope this works for you!