Routines
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90CC: Check Player In Range
Used by the routines at HandlerDoorExit, CheckDoorKey and FallThroughTrapdoor.
Checks whether the player is close to the entity of a door. It is only checked when the player is a character and the bottom four bits of offset 02 of the player are zero. The player is in range when it is to the right of the position of the entity by less than the range along the X axis, and above it by less than the range along the Y axis. The range along the X axis is halved if the attribute of the entity is bright, and the range along the Y axis is halved if it is not.
Input
B The range along the Y axis
C The range along the X axis
IX The entity
Output
F The carry flag is set if the player is in range
CheckPlayerInRange 90CC LD A,($EA92) Fetch offset 02 of the player.
90CF AND %00001111 Keep only bits 0-3.
90D1 RET NZ Return if they are not all zero.
90D2 LD A,($EA90) Fetch the sprite ID of the player from Player.
90D5 DEC A Subtract one to get the ID that starts at zero.
90D6 CP $30 Return if the player is not a character.
90D8 RET NC
90D9 BIT 6,(IX+$05) Jump to CheckPlayerInRange_X if the attribute of the entity is not bright.
90DD JR Z,CheckPlayerInRange_X
90DF SRL C Halve the range along the X axis.
CheckPlayerInRange_X 90E1 LD A,($EA93) Fetch the X position of the player from EA93.
90E4 SUB (IX+$03) Subtract the X position of the entity.
90E7 CP C Return if the player is not in range.
90E8 RET NC
90E9 BIT 6,(IX+$05) Jump to CheckPlayerInRange_Y if the attribute of the entity is bright.
90ED JR NZ,CheckPlayerInRange_Y
90EF SRL B Halve the range along the Y axis.
CheckPlayerInRange_Y 90F1 LD A,($EA94) Fetch the Y position of the player from EA94.
90F4 SUB (IX+$04) Subtract the Y position of the entity.
90F7 NEG Negate the result.
90F9 CP B Compare it with the range.
90FA RET Return.
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