4cade/src/prelaunch/skyfox.a

;license:MIT
;(c) 2019-2022 by qkumba/Frank M.

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

    !source "src/prelaunch/common.a"

         jmp   +

callback2
         jsr   $BC03
         lda   #$85
         ldx   #$A5
         cmp   $7FB5
         bne   plane
         stx   $7FB5      ; patch - don't increase damage
         stx   $9327      ; patch - don't decrease fuel

plane
         cmp   $9BC7
         bne   nopatch
         stx   $156A      ; patch - don't decrease fuel
         stx   $9281      ; patch - don't decrease fuel
         stx   $9BC7      ; patch - don't increase damage

callback1
         sec
         sbc   #8
         cmp   #2

nopatch
         lda   #0
         rts

+
         +ENABLE_ACCEL
         inc   $80        ; requires a non-zero value for the RNG
         lda   #$60
         sta   $7E3A
         jsr   $4635

         ldx   #$82       ; READ_ROM_NO_WRITE
         stx   $101
         ldx   #$A6
         stx   $104
         ldx   #$FA
         stx   $105       ; update TR hook to reboot
         sta   $5FFC
         sty   $5FFD      ; moved to LC $FFFC/D

         lda   #$4C
         sta   $6872
         lda   #<callback1
         sta   $6873
         sty   $6874
         lda   #$B0
         sta   $685B
         lda   #$90
         sta   $6862
         +READ_RAM2_NO_WRITE
         lda   MachineStatus
         and   #CHEATS_ENABLED
         beq   +
         lda   #<callback2
         sta   $8882
         sty   $8883
+
         jsr   DisableAccelerator
         +READ_ROM_NO_WRITE
         jmp   $67BD

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