Routines
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CEDB: Note Wall Contact
Used by the routine at NextStep.
Used when the ship has touched the side of a segment. For a segment that has a horizontal step the remaining length is limited to two steps if the slope goes the way that the tile is facing. If the ship has not touched a segment already the routine finds the screen address of the start with FindSegmentAddress and clears the first byte of the record. It carries on at FinishStep_Count.
NoteWallContact CEDB LD A,($CE59) The horizontal step copy.
CEDE AND A Jump to NoteWallContact_Check if A is zero.
CEDF JR Z,NoteWallContact_Check
CEE1 LD A,($5C1D) The tile number.
CEE4 BIT 1,A Jump to NoteWallContact_Right if bit 1 of A is set.
CEE6 JR NZ,NoteWallContact_Right
CEE8 LD A,($E41B) The slope direction.
CEEB CP $01 Jump to NoteWallContact_Check if A is not 01.
CEED JR NZ,NoteWallContact_Check
NoteWallContact_Limit CEEF LD A,C A=C.
CEF0 CP $02 Jump to NoteWallContact_Check if A is less than 02.
CEF2 JR C,NoteWallContact_Check
CEF4 LD C,$02 C=02.
CEF6 JR NoteWallContact_Check Jump to NoteWallContact_Check.
NoteWallContact_Right CEF8 LD A,($E41B) The slope direction.
CEFB CP $FF Jump to NoteWallContact_Check if A is not FF.
CEFD JR NZ,NoteWallContact_Check
CEFF JR NoteWallContact_Limit Jump to NoteWallContact_Limit.
NoteWallContact_Check CF01 LD A,($5C2F) The flagged steps.
CF04 AND A Jump to FinishStep_Count if A is not zero.
CF05 JP NZ,FinishStep_Count
CF08 EXX Switch to the alternate registers.
CF09 CALL FindSegmentAddress Call FindSegmentAddress.
CF0C XOR A Clear A.
CF0D LD (IX+$01),A Write A to offset 01 of IX.
CF10 EXX Switch to the alternate registers.
CF11 JP FinishStep_Count Jump to FinishStep_Count.
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