Krakout: Compute an object's spawn position

C5C4: Compute an object's spawn position

Computes a spawn position for an object into the work X and work Y, from an entry of the current level's spawn-cell table. It draws nothing.
Each table entry packs one cell of the brick grid as a column and a row. The spawn position is that cell's on-screen position, mirrored when the bat is on the left.
calc_spawn_coords	C5C4	PUSH BC	Index the current level's 4-entry spawn-cell table, 4 bytes per level.
	C5C5	LD A,(level)
	C5C8	LD L,A
	C5C9	LD H,$00
	C5CB	ADD HL,HL
	C5CC	ADD HL,HL
	C5CD	LD DE,spawn_cell_table
	C5D0	ADD HL,DE
	C5D1	LD A,(spawn_fixed_pos)	Fixed-position flag set: use the table's first entry.
	C5D4	OR A
	C5D5	JR Z,calc_spawn_coords_0
	C5D7	LD E,$00
	C5D9	JR calc_spawn_coords_1
calc_spawn_coords_0	C5DB	CALL next_random	Flag clear: pick a random entry 0–3.
	C5DE	AND $03
	C5E0	LD E,A
calc_spawn_coords_1	C5E1	LD D,$00	Read the chosen packed cell.
	C5E3	ADD HL,DE
	C5E4	LD A,(HL)
	C5E5	LD B,$00	Split the cell number into its row, counted in B, and its column, the remainder left in A.
calc_spawn_coords_2	C5E7	CP $09
	C5E9	JR C,calc_spawn_coords_3
	C5EB	SUB $09
	C5ED	INC B
	C5EE	JR calc_spawn_coords_2
calc_spawn_coords_3	C5F0	EX AF,AF'	Stash the column, then turn the row into the work Y, 16 pixels per row below the field's top edge.
	C5F1	LD A,B
	C5F2	ADD A,A
	C5F3	ADD A,A
	C5F4	ADD A,A
	C5F5	ADD A,A
	C5F6	ADD A,$20
	C5F8	LD (work_y),A
	C5FB	LD A,(bat_side)	Bat on the left? Mirror the column.
	C5FE	OR A
	C5FF	JR NZ,calc_spawn_coords_4
	C601	EX AF,AF'	Bat on the right: turn the column into the work X, then return.
	C602	ADD A,A
	C603	ADD A,A
	C604	ADD A,A
	C605	ADD A,A
	C606	ADD A,$10
	C608	LD (work_x),A
	C60B	POP BC
	C60C	RET
calc_spawn_coords_4	C60D	EX AF,AF'	Bat on the left: count the column from the far side, then turn it into the work X. That mirrors the column.
	C60E	LD B,A
	C60F	LD A,$08
	C611	SUB B
	C612	ADD A,A
	C613	ADD A,A
	C614	ADD A,A
	C615	ADD A,A
	C616	ADD A,$60
	C618	LD (work_x),A
	C61B	POP BC
	C61C	RET

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