Galaga

References

1. ^ abGalaga awards extra fighters at a first and a second score set by DIP switches, and with some settings again at every interval after the second, the interval being the second score: one setting gives 20,000, 70,000, and every 70,000 points. The three switches index one of two 8-entry tables, picked by bit 2 of the starting-fighter setting. In the first, five settings repeat, two award only the first two scores, and one awards none; in the second, every first score is 30,000, three settings repeat, four award at most the first two, and one awards none. The source reassembles MAME's galaga set, Namco rev. B.Codeneiderm/arcaderevised
   How we know

   1995; Bonus Ships Awarded (DSWB)
   ⋮
   1997; 0x20  20-60-60     ON  ON  OFF    1
   1998; 0x10  20-70-70     ON  OFF ON     2
   ⋮
   2002; 0x18  20-60        OFF OFF ON     6
   2003; 0x38  30-80        OFF OFF OFF    7
   2004; 0x00  None         ON  ON  ON     0
   2005; Bonus config displayed in following format:
   2006; 1ST BONUS  X0000 PTS
   2007; 2ND BONUS XX0000 PTS
   2008; AND EVERY XX0000 PTS
   

   2010l_38AB:
   2011       ld   hl,#_sfr_dsw4                         ; bonus levels
   ⋮
   2023       and  #0x07
   2024       jp   z,l_392D
   ⋮
   2026       ld   c,a
   2027       ld   a,(b_mchn_cfg_nships)                 ; Bonus levels depend upon number of fighters starting.
   2028       and  #0x04                                 ; note: num_ships = mchn_cfg_nships + 1
   2029       add  a,a
   2030       add  a,c                                   ; add dsw value
   2031       add  a,a                                   ; a:=a*2 ... use as offset into table
   2032       ld   hl,#str_3AA4                          ; bonus config data
   2033       rst  0x10                                  ; HL += A...A==2,C,4,6,E,8,A
   ⋮
   

   2529str_3AA4:
   2530       .db 0xFF,0xFF        ;; NO BONUS SHIPS GIVEN WITH THIS SETTING
   2531       .db 0x02,0x06
   2532       .db 0x02,0x07
   2533       .db 0x02,0x08
   2534       .db 0x03,0x0A
   2535       .db 0x03,0x0C
   2536       .db 0x02,0x06 + 0x80 ;; bit-7 means there's no 'and-every' bonus
   2537       .db 0x03,0x08 + 0x80 ;; bit-7 means there's no 'and-every' bonus
   ⋮
   2540str_3AB4:
   2541       .db 0xFF,0xFF,0x03,0x0A,0x03,0x0C,0x03,0x0F,0x03,0x8A,0x03,0x8C,0x03,0x8F,0x03,0xFF
   

   265; if bit 7 is set, the third bonus award does not apply
   

   ; looks like a bonus may be awarded. … ; actv_plyr_state[0x1E] += mchn_cfg_bonus[1] … ; sound-fx count/enable registers, bonus ship awarded sound (set non-zero) … ; new spare ship added

   The following binary files (Namco rev. B):

   Checked against the evidence by its author, an AI model, 2026-10-25.

   Checked by a second AI model, 2026-10-21.

   Revised after a check by a second AI model, 2026-10-25.

   In the claim ledger

2. ^Every fourth stage of Galaga is a challenging stage: at each stage's start stg_init_splash adds 1 to the stage counter and stores (counter + 1) mod 4, and a 0 there marks a challenge, so the counter values 3, 7, 11, … bring one.Codeneiderm/arcade
   How we know

   180;; stg_splash_scrn()
   ⋮
   183;;   Increments stage_ctr (and dedicated challenge stage %4 indicator)
   ⋮
   191; plyr_state_active.stage_ctr++
   192       ld   hl,#ds_plyr_actv +_b_stgctr           ; ++
   193       inc  (hl)
   ⋮
   195; plyr_state_active.not_chllng_stg = *HL & 0x03  ... gives 0 for challenge stage
   196       ld   a,(hl)
   197       inc  a
   198       and  #0x03
   199       ld   (ds_plyr_actv +_b_not_chllg_stg),a    ; ==(stg_ctr+1)%4 ...i.e. 0 if challenge stage
   

   1443; challenge stage e.g. 3,8,10 etc. 8 unique challenge stages.
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger