Missions: THERE

       Name: THERE                                                   [Show more]
       Type: Subroutine
   Category: Missions
    Summary: Check whether we are in the Constrictor's system in mission 1
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * Main game loop (Part 4 of 6) calls THERE


 The stolen Constrictor is the target of mission 1. We finally track it down to
 the Orarra system in the second galaxy, which is at galactic coordinates
 (144, 33). This routine checks whether we are in this system and sets the C
 flag accordingly.


 Returns:

   C flag               Set if we are in the Constrictor system, otherwise clear


.THERE

 LDX GCNT               ; Set X = GCNT - 1
 DEX

 BNE THEX               ; If X is non-zero (i.e. GCNT is not 1, so we are not in
                        ; the second galaxy), then jump to THEX

 LDA QQ0                ; Set A = the current system's galactic x-coordinate

 CMP #144               ; If A <> 144 then jump to THEX
 BNE THEX

 LDA QQ1                ; Set A = the current system's galactic y-coordinate

 CMP #33                ; If A = 33 then set the C flag

 BEQ THEX+1             ; If A = 33 then jump to THEX+1, so we return from the
                        ; subroutine with the C flag set (otherwise we clear the
                        ; C flag with the next instruction)

.THEX

 CLC                    ; Clear the C flag

 RTS                    ; Return from the subroutine