4cade/src/demo/battlezone.a

;license:MIT
;(c) 2021-2022 by Frank M., qkumba

!cpu 6502
!to "build/DEMO/BATTLEZONE#060300",plain
*=$300

         !source "src/constants.a"   ; no code in these
         !source "src/macros.a"

         ;+ENABLE_ACCEL   ; can't
         +LOAD_XSINGLE title

         lda   #$60
         sta   $201e
         jsr   $2000      ; decompress

         ldx   #0
         stx   $0811
         inx
         stx   $0816      ; reset vector patch

         ldx   #3-1
-        lda   #$EA
         sta   $1632,x    ; disable clearing keyboard strobe
         lda   patch,x
         sta   $0872,x
         sta   $161A,x
         sta   $7661,x
         sta   $766C,x
         sta   $7693,x
         sta   $0B6A,x
         sta   $73A7,x
         sta   $168F+4,x
         dex
         bpl   -

         ldx   #4-1
-        lda   patch2,x
         sta   $168F,x    ; set exits
         dex
         bpl   -

         lda   #$D0
         sta   $7733
         sta   $774D
         sta   $78B8
         sta   $78BB
         sta   $7815
         sta   $5180
         sta   $5576
         sta   $0B8E      ; disable sound

         ;+DISABLE_ACCEL

         jmp   $810

patch    !byte $4C,$00,$01
patch2   !byte $C9,$FF,$F0,$16

title    !byte x_e-x_b
x_b      !text "BATTLEZONE"
x_e

!if * > $3F0 {
  !error "code is too large, ends at ", *
}