4cade/src/prelaunch/viper.patrol.a

;license:MIT
;(c) 2022 by qkumba

!cpu 6502
!to "build/PRELAUNCH.INDEXED/VIPER.PATROL",plain
*=$106

         !source "src/prelaunch/common.a"

         lda   #$4C
         sta   $948E
         lda   #<callback1
         sta   $948F
         lda   #>callback1
         sta   $9490
         jmp   $5200      ; load "DOS"

callback1
         +ENABLE_ACCEL

         lda   #0
         sta   $56
         jsr   $BDAC      ; decompress
         lda   $1B82
         cmp   #$4C
         bne   +
         lda   #<callback2
         sta   $1B83
         lda   #>callback2
         sta   $1B84
         lda   #<callback3
         sta   $1BCA
         lda   #>callback3
         sta   $1BCB
+
         +DISABLE_ACCEL

         lda   #0
         rts

callback2
         lda   #$A5
         sta   $B7D       ; patch - don't increase lives
         sta   $B8B       ; patch - don't decrease lives
         lda   #$EA
         sta   $C39       ; patch - don't decrease fuel
         bne   +

callback3
         dec   $100C      ; patch - don't increase lives
         dec   $101A      ; patch - don't decrease lives
+        jmp   $800

!if * > $1C0 {
  !error "code is too large, ends at ", *
}