river-raid: Routine at 6268

6268: Check collision with explosion fragments

Used by the routine at check_missile_vs_objects.
Iterates through exploding_fragments (exploding_fragments) to check if the entity collides with any active debris. Each fragment entry is 3 bytes: X, Y, and type/state. Collision uses 8x8 bounding box for the entity and 16x8 for fragments. Result stored in collision_coordinates: $02 = collision detected, $00 = no collision (end of list reached).
check_fragment_collision	6268	LD HL,($5F62)	Load fragment coordinates (C=X, B=Y) from list pointer exploding_fragments_ptr and advance by 3.
	626B	LD C,(HL)
	626C	INC HL
	626D	LD B,(HL)
	626E	INC HL
	626F	INC HL
	6270	LD ($5F62),HL	Store updated pointer; copy X to A for marker check.
	6273	LD A,C	Store updated pointer; copy X to A for marker check.
	6274	CP $00	If empty slot, skip to next fragment.
	6276	JP Z,check_fragment_collision	If empty slot, skip to next fragment.
	6279	CP $FF	If end-of-set marker, jump to check_fragment_collision_end (no collision).
	627B	JP Z,check_fragment_collision_end
	627E	CALL advance_object	Adjust Y coordinate for scrolling.
Y-axis collision check (8-pixel height for both entity and fragment).
	6281	LD DE,($5EF3)	Check if entity_Y + 8 >= fragment_Y; if not, next fragment.
	6285	LD A,D
	6286	ADD A,$08
	6288	LD H,$00
	628A	LD L,A
	628B	LD D,$00
	628D	OR A
	628E	LD E,B
	628F	SBC HL,DE
	6291	JP M,check_fragment_collision	(continued).
	6294	LD A,B	Check if fragment_Y + 8 >= entity_Y; if not, next fragment.
	6295	ADD A,$08
	6297	LD H,$00
	6299	LD L,A
	629A	LD E,D
	629B	LD D,$00
	629D	OR A
	629E	SBC HL,DE
	62A0	JP M,check_fragment_collision
X-axis collision check (8-pixel width for entity, 16-pixel for fragment).
	62A3	LD DE,($5EF3)	Check if entity_X + 8 >= fragment_X; if not, next fragment.
	62A7	LD H,$00
	62A9	LD A,E
	62AA	ADD A,$08
	62AC	LD L,A
	62AD	LD D,$00
	62AF	LD E,C
	62B0	OR A
	62B1	SBC HL,DE
	62B3	JP M,check_fragment_collision	(continued).
	62B6	LD A,C	Check if fragment_X + 16 >= entity_X; if not, next fragment.
	62B7	ADD A,$10
	62B9	LD DE,($5EF3)
	62BD	LD H,$00
	62BF	LD L,A
	62C0	OR A
	62C1	LD D,$00
	62C3	SBC HL,DE
	62C5	JP M,check_fragment_collision
Collision detected with fragment.
	62C8	LD A,$02	Store $02 (collision) to collision_coordinates and return.
	62CA	LD ($5F8B),A
	62CD	RET