Routines
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54705: Remove Entity from List
Used by the routines at Process_Enemy_Entity, Handle_Homing_Enemy, Kill_Wall_Bouncing_Enemy and Process_Final_Phase_Enemy_Entity.
Removes the entity whose record is pointed to by Entity_Record_Pointer from the entity list. Steps back to the start of the entity's 12-byte record, then block-copies all subsequent records down by 12 bytes via LDIR, closing the gap. The entity list end pointer at Playfield_Entity_List_Pointer is decremented by 12 to reflect the shorter list. Returns with HL pointing to the record that now occupies the removed entity's slot.
Remove_Entity_From_List 54705 LD HL,(50394) Load the entity record pointer from Entity_Record_Pointer.
This entry point is used by the routines at Kill_Tracked_Enemy_Entity and Process_Cluster_Entity.
Remove_Entity_From_List_Step 54708 DEC HL Step back to the start of the entity record and save the updated pointer to Entity_Record_Pointer.
54709 DEC HL
54710 LD (50394),HL
54713 LD DE,12 Compute the start of the next entity record (12 bytes ahead) in DE.
54716 ADD HL,DE
54717 EX DE,HL
54718 LD HL,(50385) Load the entity list end pointer from Playfield_Entity_List_Pointer, subtract the destination address to get the copy byte count, and load that count into BC.
54721 SBC HL,DE
54723 INC HL
54724 INC HL
54725 INC HL
54726 LD B,H
54727 LD C,L
54728 LD HL,(50394) Set source to the start of the next entity record and shift all remaining records down by 12 bytes via LDIR.
54731 EX DE,HL
54732 LDIR
54734 LD HL,(50385) Decrement the entity list end pointer at Playfield_Entity_List_Pointer by 12 bytes and return with HL pointing to the new occupant of the vacated slot.
54737 LD DE,12
54740 SBC HL,DE
54742 LD (50385),HL
54745 LD HL,(50394)
54748 RET Return.
Entity movement handler, stored as the entity handler address in entity records that use the narrow sprite renderer. Applies the entity's velocity to its current screen position, validates that the new position lies within the playfield bounds, updates the entity record, and redraws the sprite. If the new position is out of bounds the entity is removed via Remove_Entity_From_List.
Move_And_Redraw_Entity 54749 LD (50394),HL Save the entity record pointer to Entity_Record_Pointer.
54752 CALL Erase_Narrow_Entity_Sprite Erase the entity's current sprite via Erase_Narrow_Entity_Sprite.
54755 LD HL,(50394) Reload the entity record from Entity_Record_Pointer and point HL at the Y position field; copy the pointer to DE.
54758 INC HL
54759 INC HL
54760 INC HL
54761 LD D,H
54762 LD E,L
54763 INC DE Advance DE to the Y velocity field and add the velocity to the current Y position.
54764 INC DE
54765 INC DE
54766 INC DE
54767 LD A,(DE)
54768 ADD A,(HL)
54769 CP 16
54771 JR C,Remove_Entity_From_List Reject the move if the new Y position is above the playfield top edge (16).
54773 CP 184
54775 JR NC,Remove_Entity_From_List Reject the move if the new Y position is below the playfield bottom edge (184).
54777 LD (HL),A Store the new Y position; advance to the X fields and add the X velocity to the current X position.
54778 LD B,A
54779 INC DE
54780 INC HL
54781 LD A,(DE)
54782 ADD A,(HL)
54783 CP 8 Reject the move if the new X position is past the left edge (8).
54785 JR C,Remove_Entity_From_List Remove the entity if the new X position is too close to the left wall.
54787 CP 248 Reject the move if the new X position is past the right edge (248).
54789 JR NC,Remove_Entity_From_List Remove the entity if the new X position is too close to the right wall.
54791 LD (HL),A Store the new X position; step back and update the two additional entity record fields from their corresponding velocity bytes.
54792 DEC HL
54793 DEC HL
54794 LD A,(DE)
54795 ADD A,(HL)
54796 LD (HL),A
54797 DEC HL
54798 DEC DE
54799 LD A,(DE)
54800 ADD A,(HL) Update the final position field and step back to the entity record origin.
54801 LD (HL),A
54802 DEC HL
54803 EXX Set the entity colour to INK: WHITE, PAPER: BLACK (BRIGHT) in B' and redraw the sprite via Draw_Narrow_Entity_Sprite.
54804 LD B,71
54806 EXX
54807 CALL Draw_Narrow_Entity_Sprite
54810 LD HL,(50394) Reload the entity record pointer from Entity_Record_Pointer.
54813 JP Advance_Entity_Pointer Jump to the entity update completion handler at Advance_Entity_Pointer.
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