Routines
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8401: Main loop
This is called the "main loop" because it does all of the driving of the primary game functions, but it's really a subroutine of the boostrap / uber main loop above.
Input
Used by the routines at bootstrap and handle_perp_caught.
main_loop 8401 CALL load_stage Call load_stage
8404 LD A,($8007) Jump to ml_not_credits if we're not on the end screen (stage 6)
8407 CP $06
8409 JR NZ,ml_not_credits
Run the end screen.
ml_run_end_screen 840B CALL $5C00 Call the end screen animation routine
840E LD HL,$8007 Reset (wanted) stage to 1
8411 LD (HL),$01
8413 PUSH HL Call load_stage
8414 CALL load_stage
8417 POP HL
8418 LD (HL),$06 Set (wanted) stage to 6 [not sure why]
841A RET Return
Run the main game loop.
ml_not_credits 841B CALL run_pregame_screen Call run_pregame_screen
841E LD HL,$5D1D Address of stage_set_up_data
8421 CALL set_up_stage Call set_up_stage
8424 LD HL,$A13B Cycle start_speech_cycle 3,2,1 then repeat
8427 LD A,(HL)
8428 DEC A
8429 JR NZ,ml_store_start_speech
842B LD A,$03
ml_store_start_speech 842D LD (HL),A
Choose the startup speech sample.
842E ADD A,A start_speech = (A << 2) OR 2 -- The number of leading zeroes are used to encode a delay
842F ADD A,A
8430 OR $02
8432 LD ($A26B),A
8435 LD A,($A139) Test 128K mode flag
8438 AND A
8439 LD A,$FF Set hazards[0].used to $FF -- I suspect this keeps the perp spawned
843B LD ($A188),A
843E LD HL,$81DD Address of start_stage_chatter
8441 CALL Z,start_chatter Call start_chatter if not in 128K mode (priority $FF)
ml_loop 8444 CALL drive_sfx Call drive_sfx
8447 CALL keyscan Call keyscan
844A CALL tick Call tick
844D CALL check_user_input Call check_user_input
8450 CALL read_map Call read_map
8453 CALL handle_perp_caught Call handle_perp_caught
8456 CALL move_hero_car Call move_hero_car
8459 CALL spawn_cars Call spawn_cars
845C CALL cycle_counters Call cycle_counters
845F CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
8462 CALL build_height_table Call build_height_table
8465 CALL scroll_horizon Call scroll_horizon
8468 CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
846B CALL layout_road Call layout_road
846E CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
8471 CALL draw_road Call draw_road
8474 CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
8477 CALL layout_objects Call layout_objects
847A CALL prepare_tunnel Call prepare_tunnel
847D CALL spawn_hazards Call spawn_hazards
8480 CALL drive_helicopter Call drive_helicopter
8483 CALL choose_dirt_and_stones Call choose_dirt_and_stones
8486 CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
8489 CALL draw_hazards Call draw_hazards
848C CALL layout_dirt_and_stones Call layout_dirt_and_stones
848F CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
8492 CALL move_helicopter Call move_helicopter
8495 CALL check_collisions Call check_collisions
8498 CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
849B CALL draw_everything_else Call draw_everything_else
849E CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
84A1 CALL animate_hero_car Call animate_hero_car
84A4 CALL speed_score Call speed_score
84A7 CALL update_scoreboard Call update_scoreboard
84AA CALL calc_overtake_bonus Call calc_overtake_bonus
84AD CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
84B0 CALL drive_chatter Call drive_chatter
84B3 CALL draw_smash_bar Call smash_bar_etc
84B6 CALL transition Call transition
84B9 CALL play_engine_or_siren_sfx_hook Call play_engine_or_siren_sfx_hook
84BC CALL draw_screen Call draw_screen
84BF CALL exit_fork Call exit_fork
84C2 LD A,($8000) Is test mode enabled?
84C5 AND A If not, goto not_test_mode
84C6 JR Z,ml_not_test_mode
Test mode handling
ml_handle_test_mode 84C8 LD A,$F7 Read keys 1/2/3/4/5
84CA IN A,($FE)
84CC CPL Change to active high
84CD AND $1F Mask off just keys
84CF JR Z,ml_not_test_mode If none are set then jump
84D1 EX AF,AF' Bank key flags
84D2 LD BC,$0804 Effect 8 (bip), Priority 4
84D5 CALL start_sfx Call start_sfx
84D8 CALL silence_audio_hook Call silence_audio_hook
84DB EX AF,AF' Unbank key flags
84DC RRA Is bit 0 set? (key 1 to restart the level)
84DD JP C,main_loop Restart level if so
84E0 LD HL,$8007 HL = &wanted_stage_number
84E3 RRA Is bit 1 set? (key 2 to load the next level)
84E4 JR NC,ml_check_for_3 Jump if NOT
84E6 INC (HL) wanted_stage_number++
84E7 JP main_loop Loop to main_loop
ml_check_for_3 84EA RRA Is bit 2 set? (key 3 to load the end screen)
84EB JR NC,ml_increment_credits Jump if NOT
84ED LD (HL),$06 wanted_stage_number = 6
84EF JP main_loop Loop to main_loop
ml_increment_credits 84F2 LD HL,$A13D Increment credits unless maxed out at 9
84F5 LD A,(HL)
84F6 CP $09
84F8 JR Z,ml_not_test_mode
84FA INC (HL)
ml_not_test_mode 84FB LD A,($A231) Load transition_control
84FE AND A Jump to ml_loop if non-zero
84FF JP NZ,ml_loop
Play speech when we see a 1-bit shift out of start_speech.
8502 LD HL,$A26B Address of start_speech
8505 SRL (HL) Shift the counter right
8507 JR NC,ml_check_quit Jump if no carry
8509 LD A,(HL) Load speech sample index
850A LD (HL),$00 Zero start_speech
850C CALL play_speech_hook Call play_speech_hook
850F JP ml_loop Loop to ml_loop
ml_check_quit 8512 LD A,($A26A) Loop to ml_loop if quit_state is zero
8515 AND A
8516 JP Z,ml_loop
Quitting the game is in progress.
8519 DEC A Decrement quit_state
851A JP NZ,escape_scene Jump to escape_scene if non-zero
851D LD A,$02 quit_state = 2
851F LD ($A26A),A
8522 LD A,$08 Forward transition
8524 CALL setup_transition Call setup_transition
8527 JP ml_loop Loop to ml_loop
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