Routines
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33421: BuildDuctExitList
The duct view's "move to:" rows: fill strip cells 2-5 from the room's four RoomAdjDucts slots (skipping no-exit entries), then overwrite each present exit with an anonymous direction arrow — strings 57-60 "North/East/South/West" — so the player sees where the crawlway leads but not what it leads to.
33421 LD A,(31242) HL = RoomAdjDucts + room * 5
33424 AND 63
33426 LD L,A
33427 LD H,0
33429 PUSH HL
33430 ADD HL,HL room*5 = room*4 + room
33431 ADD HL,HL
33432 POP DE
33433 ADD HL,DE
33434 LD DE,29346 RoomAdjDucts
33437 ADD HL,DE
33438 LD DE,29632 DE -> strip cell 2
33441 LD B,4 four duct directions:
33443 LD C,(HL) C = the destination that way;
33444 CP C own room = no exit: leave the
33445 JR Z,33457 cell empty (checked twice — A
33447 LD A,(31242) holds a stale destination after
33450 AND 63 a stored exit, so the reload
33452 CP C makes the second test reliable)
33453 JR Z,33457
33455 LD A,C else cell = the destination room
33456 LD (DE),A
33457 INC DE
33458 INC HL
33459 DJNZ 33443
33461 LD B,4 second pass: disguise each
33463 LD HL,29632 present exit as a direction
33466 LD C,57 arrow (57 North ... 60 West)
33468 LD A,(HL)
33469 CP 255
33471 JR Z,33474
33473 LD (HL),C
33474 INC C
33475 INC HL
33476 DJNZ 33468
33478 RET
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