Fixes to Aga Tower staircases

Lots of initial work on key doors and other door pairs

asm/keydoors.asm

@@ -15,3 +15,43 @@ dw $3882, $3660, $1e81
 org $1fd974 ;(PC: 0fd974) TT Bossway 0xbc
 dw $1c82, $0081
 
+; code to un-pair or re-pair doors
+
+; doorlist is loaded into 19A0 but no terminator
+; new room is in A0
+; for "each" door do the following: (each could mean the first four doors?)
+; in lookup table, grab room and corresponding position
+; find the info at 7ef000, x where x is twice the paired room
+; check the corresponding bit (there are only 4)
+; set the bit in 068C
+
+; Note the carry bit is used to indicate if we should aborted (set) or not
+CheckIfDoorsOpen: {
+    jsr TrapDoorFixer ; see normal.asm
+    ; note we are 16bit mode right now
+    lda $040c : cmp #$00ff ;: bne .gtg
+    lda $a0 : dec : tax : and #$000f ; hijacked code
+    sec : rtl ; set carry to indicate normal behavior
+
+    .gtg
+    phb : phk : plb
+    stx $00 : ldy #$00 : stz $03
+    .nextDoor
+    lda $a0 : asl : tax
+    lda KeyDoorOffset, x : beq .skipDoor
+    asl : sty $05 : !add $05 : tax
+    lda PairedDoorTable, x : beq .skipDoor
+    sta $02 : and #$00ff : asl a : tax
+    lda $7ef000, x : and #$f000 : and $03 : beq .skipDoor
+    tyx : lda $068c : ora $0098c0,x  : sta $068c
+    .skipDoor
+    iny #2 : cpy $00 : bne .nextDoor
+    plb : clc : rtl
+}
+
+; outstanding issues
+; how to indicate opening for other (non-first four doors?)
+; Bank01 Door Register stores the 4 bits in 068c to 400 (depending on type)
+; Key collision and others depend on F0-F3 attribute not sure if extendable to other numbers
+; Dungeon_ProcessTorchAndDoorInteractives.isOpenableDoor is the likely culprit fo collision problems
+; Saving open status to other unused rooms is tricky -- Bank 2 13947 (line 8888)