If you press e on doors with crystals embedded, inventory should open, then you need to put crystal with matching color in it.
note that you cannot open skull door yet.
Thanks for playing.
OK, thanks :)
Nice game with a lot of content. While a bit rough, I had a nice time, a bit too difficult on the jump part but it's hard to find the right balance in such a short period of time.
And I quite liked the easter eggs :)