>> Flip overlays. Enter code in that order.
>> Enter "37854"

Wha--that's right! The TRANSPARENT OVERLAY with a 1 on it was found on the floor next to the FURNACE. What if...what if it was upside-down when you found it? It is transparent, after all--there's no way to tell which way is up for a number like 1, which is basically a straight line. You flip the #1 TRANSPARENT OVERLAY over and combine them again.

The new resulting number, 37854, is divisible by 3. You enter it into the KEYPAD.

It--it works!! You've finally opened this blasted door!

>> Screw the rules, Jimmy's got money.

Thank god for Microsoft Flight Simulator! YGO:TAS is like your favorite online series ever, and you've taken it upon yourself to memorize almost all of the episodes. Oh my god a giant rock! All of this is, of course, completely irrelevant to the task at hand.

The DOORWAY opens into the other section of BURAM CASTLE, which appears to be broken up into rooms, not unlike a HOUSE. You walk up and down the initial HALLWAY without actually going anywhere. On ground level, where you are, there appears to be two open DOORWAYS, one PINKISH LOCKED DOOR with no handle, and a STAIRWELL leading upward.