The Wonderland Board

I'm stuck in Qwertyx with one key too few. I just finished Crystal Castle and when I walk maround I can see one more star (small yellow one, that is) indicating a puzzle to be done. But I can't get to it as it's blocked by a grey/blue gate. But I have no key. What now?

You have missed some other level, there has to be something that will give you the blue key.

Have you found a level called "What the Blink?", that one is easier to miss than most.