river-raid: Routine at 5D44

5D44: Initialize game state for overview/demo mode.

Used by the routines at start_gameplay_or_overview, start_overview and start_gameplay.
This routine sets up the initial game state used by the overview (attract mode) routine. It initializes player positions, scores, lives, terrain state, and sets the gameplay mode to GAMEPLAY_MODE_OVERVIEW.
init_state	5D44	LD A,$78	Initialize plane X position to $78. Why isn't it $80?
	5D46	LD ($5F72),A	Initialize plane X position to $78. Why isn't it $80?
	5D49	CALL init_starting_bridge	Set starting bridges for both players based on game mode.
	5D4C	LD HL,$5F00	Initialize viewport objects list (set pointer, mark as empty).
	5D4F	LD ($5F60),HL
	5D52	LD (HL),$FF
	5D54	LD A,$1F	Set normal activation timing (every 32 frames).
	5D56	LD ($5F5F),A	Set normal activation timing (every 32 frames).
	5D59	LD A,$00	Set border to black, silence speaker, clear tank shell and controls state.
	5D5B	OUT ($FE),A
	5D5D	LD ($5EF2),A
	5D60	LD ($6BB0),A
	5D63	LD BC,$4C83	Initialize terrain element (C=$83: river center position, B=$4C: row offset).
	5D66	LD ($5F78),BC
	5D6A	LD A,$02	Initialize terrain profile, gameplay mode, and speed to $02 (GAMEPLAY_MODE_OVERVIEW / SPEED_NORMAL).
	5D6C	LD ($5F77),A
	5D6F	LD ($5F68),A
	5D72	LD ($5F64),A
	5D75	LD ($5F6D),A	Store $02 to state_bridge_destroyed (unclear why $02 is used here).
	5D78	LD HL,"0"	Initialize all player scores to zero.
	5D7B	LD ($90BC),HL
	5D7E	LD ($90BE),HL
	5D81	LD ($90C0),HL
	5D84	LD ($90C2),HL
	5D87	LD ($90C4),HL
	5D8A	LD ($90C6),HL
	5D8D	LD A,$01	Set level fragment number and terrain position to 1.
	5D8F	LD ($5F76),A
	5D92	LD ($5F7D),A
	5D95	LD HL,$0404	Set both players' lives to 4.
	5D98	LD ($923B),HL	Set both players' lives to 4.
	5D9B	LD ($923D),A	Set current player to PLAYER_1.
	5D9E	RET