4cade/src/demo/apple.oids.a

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

!cpu 6502
!to "build/DEMO/AO#06B900",plain
*=$B900

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

         +ENABLE_ACCEL_LC
         +LOAD_XSINGLE title

         lda   #$60
         sta   $604E
         jsr   $6000      ; decompress

         lda   #$4C
         sta   $4FD7      ; exit on keypress
         sta   $4F96      ; exit at end of demo
         ldx   #0
         stx   $4FD7+1
         inx
         stx   $4FD7+2

                          ; doesn't try to detect joystick or joystick buttons

         lda   #$D0       ; disable sounds
         sta   $0DA0      ; A-P-P-L-E-O-I-D-S
         sta   $1118      ; alien
         sta   $111F      ; alien

         lda   #<callback
         sta   $4F96+1
         lda   #>callback
         sta   $4F96+2    ; wait 10 seconds at end of demo once Twilight logo is shown

         +DISABLE_ACCEL
         jmp   $4D00

callback lda   $C000
         bmi   +
         lda   #$FF
         jsr   $FCA8      ; WAIT 0.16395694 seconds
         dec   count
         bne   callback
+        jmp   $100

count    !byte $3D        ; number of 0.16395694 second WAIT cycles

                          ; (A*A*2.5 + A*13.5 + 7) * 0.980 usec
                          ; 163,840 + 3,456 + 7 = 167,303 * 0.980 usec = 163,956.94 usec
                          ; 163,956.94 usec = 0.16395694 seconds
                          ; 61 cycles (hex $3D) of A=256 WAIT = 10 seconds

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

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