Routines
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B358: Move Creature Vertically
Used by the routines at Handle_Flying_Creature, Move_Creature_Horizontally, Handle_Jellyfish and Handle_Gargoyle.
Moves a creature one step closer to Sabreman's room when it is in a different room y (and the same room x). It works like Move_Creature_Horizontally but vertically. It is entered with the carry flag set if Sabreman's room y is less than the room y of the creature.
The creature is removed if the room has a floor and it is above Sabreman's room (or a ceiling and it is below), as it cannot get through. The x position is kept between 18 and E0.
Input
IX Object record
E Flags of the room that the creature is in
Move_Creature_Vertically B358 LD (IX+$0F),$01 Set the redraw flags to 01 so that the creature is drawn without being erased when it arrives.
B35C LD (IX+$0B),$00 Clear the contact flags.
B360 JR C,Move_Creature_Vertically_Move_Up Jump to Move_Creature_Vertically_Move_Up if Sabreman is above the creature.
B362 BIT 4,E Jump to Move_Creature_Horizontally_Remove_Creature if the room has a floor.
B364 JR NZ,Move_Creature_Horizontally_Remove_Creature
B366 LD A,(IX+$09) Fetch the y velocity.
B369 ADD A,$02 Accelerate downwards by adding two.
B36B BIT 7,A Jump to Move_Creature_Vertically_Store_Velocity if the y velocity is negative.
B36D JR NZ,Move_Creature_Vertically_Store_Velocity
B36F CP $31 Jump to Move_Creature_Vertically_Move_Down if the y velocity has reached 31.
B371 JR NC,Move_Creature_Vertically_Move_Down
Move_Creature_Vertically_Store_Velocity B373 LD (IX+$09),A Store the y velocity.
Move_Creature_Vertically_Move_Down B376 LD A,(IX+$09) Fetch the y velocity.
B379 SRA A Divide it by sixteen, keeping the sign.
B37B SRA A
B37D SRA A
B37F SRA A
B381 ADD A,(IX+$03) Add the y position of the creature.
B384 CP $9F Jump to Move_Creature_Vertically_Store_Y if the y position is less than 9F.
B386 JR C,Move_Creature_Vertically_Store_Y
B388 INC (IX+$04) Move the creature to the room below.
B38B LD A,$2C Set the y position to 2C.
Move_Creature_Vertically_Store_Y B38D LD (IX+$03),A Store the y position.
Keep the x position between 18 and E0.
Move_Creature_Vertically_Adjust_X B390 LD A,(IX+$01) Fetch the x position.
B393 CP $18 Jump to Move_Creature_Vertically_Test_Right if the x position is 18 or more.
B395 JR NC,Move_Creature_Vertically_Test_Right
B397 LD (IX+$01),$18 Set the x position to 18.
Move_Creature_Vertically_Test_Right B39B CP $E0 Return if the x position is less than E0.
B39D RET C
B39E LD (IX+$01),$E0 Set the x position to E0.
B3A2 RET Return.
Sabreman is above the creature.
Move_Creature_Vertically_Move_Up B3A3 BIT 0,E Jump to Move_Creature_Horizontally_Remove_Creature if the room has a ceiling.
B3A5 JP NZ,Move_Creature_Horizontally_Remove_Creature
B3A8 LD A,(IX+$09) Fetch the y velocity.
B3AB SUB $02 Accelerate upwards by subtracting two.
B3AD BIT 7,A Jump to Move_Creature_Vertically_Store_Up_Velocity if the y velocity is positive.
B3AF JR Z,Move_Creature_Vertically_Store_Up_Velocity
B3B1 CP $D0 Jump to Move_Creature_Vertically_Add_Up_Velocity if the y velocity is less than D0.
B3B3 JR C,Move_Creature_Vertically_Add_Up_Velocity
Move_Creature_Vertically_Store_Up_Velocity B3B5 LD (IX+$09),A Store the y velocity.
Move_Creature_Vertically_Add_Up_Velocity B3B8 LD A,(IX+$09) Fetch the y velocity.
B3BB SRA A Divide it by sixteen, keeping the sign.
B3BD SRA A
B3BF SRA A
B3C1 SRA A
B3C3 ADD A,(IX+$03) Add the y position of the creature.
B3C6 CP $40 Jump to Move_Creature_Vertically_Store_Up_Y if the y position is 40 or more.
B3C8 JR NC,Move_Creature_Vertically_Store_Up_Y
B3CA DEC (IX+$04) Move the creature to the room above.
B3CD LD A,$BF Set the y position to BF.
Move_Creature_Vertically_Store_Up_Y B3CF LD (IX+$03),A Store the y position.
B3D2 JR Move_Creature_Vertically_Adjust_X Jump to Move_Creature_Vertically_Adjust_X.
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