river-raid: Routines

Address	Description
5CD2	Game initialization and interrupt setup
5D06	Return to control selection dialog
5D10	Start gameplay or overview mode based on user selection
5D2B	Start overview mode
5D35	Start gameplay mode
5D44	Initialize game state for overview/demo mode.
5D9F	Decrease player 2 lives
5DA6	Initialize and start gameplay mode
5F91	Main gameplay loop
5FDA	Scan cursor keys
600A	Scan Kempston joystick
6039	Scan Sinclair joystick
6068	Scan keyboard
60A5	Render player plane and terrain fragments
6124	Calculate fuel gauge sprite offset
6136	Collision detection dispatcher
615E	Handle COLLISION_MODE_FIGHTER collision detection
61BB	Check collision against bridges and viewport objects
6249	Increment player 2's bridge counter
6256	Handle COLLISION_MODE_FUEL_DEPOT (initiate refueling)
6268	Check collision with explosion fragments
62CE	End of fragment list - no collision found
62D4	Get Y offset for balloon collision
62D7	Get Y offset for fuel depot collision
62DA	Increase vertical coordinate of the object by the value of state_speed.
62E0	Decrease vertical coordinate of the object by the value of state_speed.
62E8	Check missile collision against viewport objects
63FC	Reset gameplay mode to normal and exit collision system
6414	Handle missile hit on regular helicopter
6423	Handle missile hit on ship
6444	Handle missile hit on advanced helicopter
6453	Handle missile hit on fighter
6462	Handle missile hit on balloon
6478	Handle collision with fuel depot
649E	Jump to collision finalization
64A1	Handle refueling from fuel depot
64BC	Print current bridge number on status line
64E5	Print bridge number for Player 2
64F1	Common bridge printing for Player 2
6506	Print a space character
650A	Handle player death
6568	Restart gameplay for current player
656F	Check if Player 2 has lives remaining when Player 1 is out
6577	Game Over
6587	Setup Player 2 status line during overview mode
65AB	Switch to Player 2 after Player 1 death
65BB	Switch to Player 2 when Player 1 dies in two-player mode
65CB	Handle Player 2 death and determine next game state
65DE	Switch to Player 1 after Player 2 death
65F3	Move player plane right by 2 pixels
6630	Restore plane state after rendering
6642	Move player plane left by 2 pixels
6682	Render player plane sprite
66CC	Load banked plane sprite address
66D0	Advance game scroll and update bridge position
66EE	Update bridge Y position during scroll
6704	Clear bridge when scrolled off screen
670A	Handle up/accelerate input
6717	Handle down/decelerate input
6724	Handle fire button input
673D	Animate and render player missile
678E	Clear CONTROLS_BIT_FIRE_SOUND flag
6794	Finalize collision and erase missile sprite
6831	Add $0800 offset to screen pointer
6836	Add $1000 offset to screen pointer
683B	Scroll screen pixels vertically
68A1	Clear top screen rows after scrolling
68B7	Scroll screen attributes up by one row
68C5	Copy bottom attribute row to row 1 and refill bottom
68E9	Initialize bridge state for current player
6927	Render bridge attributes to bottom row
693C	Initialize bridge approach state
6947	Clear bridge destroyed flag
694D	Advance to next bridge/level
6963	Wrap bridge index from 49 to 1
696B	Initialize island state from terrain data
6990	Render one line of island terrain
6A3F	Calculate mirrored right edge position
6A45	Calculate offset right edge position
6A4A	Get player 2's bridge progress
6A4F	Load next terrain fragment and initialize rendering state
6AA3	Render one pixel line of terrain
6B58	Calculate mirrored right edge (terrain extras mode 1)
6B5E	Calculate offset right edge (terrain extras mode 2)
6B63	Load canal sprite (river-adjacent side)
6B6B	Load canal sprite (road-adjacent side)
6B73	Load road/bridge sprite
6B7B	Render special terrain fragment (bridge/road area)
6BB1	Keep the game paused
6BBF	Handle the Enter key pressed
6BD2	Reset to control selection screen.
6BDB	Maskable interrupt handler (IM 2)
6BED	Process control state flags and trigger sound effects
6C24	Return from interrupt handler
6C31	Play bonus life sound effect
6C52	Complete bonus life sound sequence
6C5D	Play normal speed engine sound
6C7B	Play explosion sound effect
6CAD	Complete explosion sound sequence
6CB8	Play fast speed engine sound
6CD6	Play slow speed engine sound
6CF4	Play low fuel warning sound
6D17	Level overview screen
6DDD	Reset scrolling title text
6DEB	Initializes the starting bridge based on the value of state_game_mode using starting_bridges for the lookup.
6DFF	Consume fuel and update gauge display
6E40	Add fuel during refueling
6E86	Set low fuel warning flag
6E8C	Clear low fuel warning flag
6E92	Play tank full sound
6E9C	Create explosion fragment at coordinates
6EAB	Add object entry to a set
6EBC	Write object entry to set
6EC8	Process and render all active explosions
6F63	Load frame 1/5 explosion sprite
6F67	Load frame 2/4 explosion sprite
6F6B	Load frame 3 explosion sprite
6F6F	Load explosion erasure sprite
6F73	Reset explosions set pointer
6F7A	Remove completed explosion from set
6F80	Spawn objects from level data slot
6FBB	Render rock sprite
6FE6	Load pointer to right-facing enemy sprites
6FEA	Set up object screen position for rendering
6FF6	Spawn and render enemy on screen
7038	Load ship screen attributes
703B	Load fighter screen attributes
703E	Load tank screen attributes
7046	Set XOR blending mode for sprite rendering
7051	Render fuel station
706C	Render balloon
708E	Main viewport slot processing loop.
7104	Ship or helicopter operation routine
7113	Advance left-facing ship or helicopter
7128	Continue ship/helicopter rendering
7155	Reset left-moving fighter position
7158	Fighter operation routine
716B	Continue fighter operation
7192	Advance right-facing fighter
719F	Reset right-moving fighter position
71A2	Animate tank shell explosion
720E	Finish tank shell explosion animation
7224	Handle non-activated object
7248	Load right-facing helicopter rotor sprite
724C	Animate object (helicopter rotor)
7259	Animate helicopter rotor
728B	Advance tank right by 4 pixels
7290	Signal road tank at center
7296	Tank operation routine
72E6	Set XOR/XOR blending mode
72EF	Set OR/OR blending mode
72F8	Adjust tank position for left orientation
72FD	Adjust tank position for right orientation
7302	Operate tank on river bank
7343	Initialize tank shell state
7358	Cancel and remove tank shell
735E	Check shell initialization condition
7380	Invert coordinate for position calculation
7387	Invert shell coordinate delta
738E	Invert helicopter missile offset
7393	Operate helicopter missile
73D0	Remove helicopter missile
73D8	Add X offset for right-facing missile spawn
73DD	Render helicopter missile (spawn new)
7415	Handle helicopter missile collision
7441	Operate tank shell
74A0	Erase off-screen tank shell
74C6	Trigger tank shell explosion
74E4	Remove tank shell from game
74EE	Handle tank after bridge destruction
7546	Get bridge number for player 1
754C	Operate fuel station
758A	Clip fuel station height to viewport
75A2	Advance right-facing ship or helicopter
75BA	Load enemy sprite pointer
75D0	Reverse enemy direction at river bank
7627	Reset current_slot_ptr to the start of viewport_slots.
762E	Remove an object from the viewport array.
7649	Operate balloon movement and rendering.
76AC	A useless procedure that unconditionally jumps to operate_viewport_slots.
76AF	Right-facing balloon movement.
76DA	Handle balloon terrain collision.
7804	Clear screen and enter setup menu.
7AB9	Initial game setup
7ACD	Wait until the user chooses a valid control type or switch to the overview mode on timeout.
7B07	Wait until the user chooses a valid game mode.
7B57	Switch to overview/demo mode on timeout.
8A02	Generate firing sound effect.
8A1B	Scroll the text crawl row left by 1 pixel.
8A33	Initialize UDG and screen attributes.
8A4E	Calculate screen address from pixel coordinates.
8B1E	Render a sprite at position from previous_object_coordinates.
8B3C	Render an object with collision detection.
8B70	Process one row of sprite rendering.
8B94	Adjust screen address for third-of-screen crossing.
8BA3	Process old position screen address adjustment.
8BC6	Adjust old position for third-of-screen crossing.
8C0B	Render one row of sprite data to screen.
8C1B	Self-modifying blending operation (erasure).
8C3C	Self-modifying blending operation (drawing).
8C45	Jump to collision dispatcher
90E0	Add score points for a hit target
9109	Add a life to the current player.
9122	Update and print score for current player.
913B	Increase a digit in the player 1's score.
914B	Print a digit from player 1's score.
9169	Increase a digit in the player 2's score.
9179	Print a digit from player 2's score.
9191	Handle carry for player 1's score digit.
91A9	Handle carry for player 2's score digit.
91C1	Print player 2's score on the status line.
91E8	Print player 2 score area or high score on status line.
923E	Print lives for current player.
924F	Continue printing lives after count has been loaded.
9264	Print six spaces to clear old lives display.
9277	Player 2 branch of print_lives.
928D	Set screen attributes for sprite area.
935D	Return point when attribute color is zero.
9367	Early exit from old position attribute loop.
936B	Early exit from new position attribute loop.
936F	Handle old position attributes when sprite is at screen top (row 0).
9388	Handle new position attributes when sprite is at screen top (row 0).
93A1	Compare two 6-digit scores.
93B8	Return 1 (first score less than second).
93BB	Return $FF (first score greater than second).
93BE	Update high score table from current player score.
93F2	Check if player 2 score beats player 1 score.
940A	Clear the screen by setting all pixel bytes to $00 and all attributes to the value set in D.
9423	Load pointer to current player's lives counter.