#config scanner= 1
#config weapon= 3
#config armor=1
#config engine= 3
#config heatsinks=4 
#config mines= 0
#config shield= 

#msg Watch your six! :)

        mov     ax,     1
        int     3               ; Keepshift on.
!begin
        mov     dx,     64      ; Set our scan arc to 64 degrees

!start
        opo     11,     100     ; Throttle to 90%
        opo     17,     dx      ; Set arc to DX
        ipo     7,      fx      ; Scan for enemy
        cmp     fx      2000
        ja      !decide         ; No one found? Decide what to do


!track
        ; Someone was found
        opo     11,     100     ; Throttle to 100%
        mov     bx,     dx      ; BX = DX (dx is the scan width)
        mpy     bx,     @3      ; bx = scanwidth*accuracy
        sar     bx,     1       ; bx = scanwidth*accuracy/2
        opo     12,     bx      ; turn turret by that amount.

        cmp     dx,     2       ; check scanwidth
        jbe     !fire           ; width<=2? then fire, otherwise tighten
        shr     dx,     1       ; tighten scanwidth

!fire
        opo     15,     @3      ; Fire!

        ; Set course towards target
        mov     bx,     @1      ; get current desired heading
                                ; (not actual heading)
        ipo     3,      ax      ; Get actual heading
        add     ax,     @2      ; And add to it our turret offset
                                ; AX is now our new desired heading.

        cmp     fx      120     ; Check our distance
        jae     !turn           ; Too close? If not, then steer straight
        add     ax,     64      ; if so, veer off
!turn
        and     ax,     255     ; Fix ax into 0-255.
        sub     ax,     bx      ; get number of degrees to turn.
        opo     14,     ax      ; turn!

        jmp     !start          ; start over


;Decides what to do if no one found
!decide
        cmp     dx      64      ; Compare scanwidth to 64
        jae     !flip           ; If above, then flip
        shl     dx      1       ; otherwise, widen arc
        jmp     !start          ; start over
!flip
        opo     12      128     ; rotate turret 128 degrees (180).
        opo     14      8       ; Turn slightly
;        jmp     !start          ; start over
;program starts over automatically when it runs past the end.