Flight: OUCH

       Name: OUCH                                                    [Show more]
       Type: Subroutine
   Category: Flight
    Summary: Potentially lose cargo or equipment following damage
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * OOPS calls OUCH


 Our shields are dead and we are taking damage, so there is a small chance of
 losing cargo or equipment.


.OUCH

 JSR DORND              ; Set A and X to random numbers

 BMI out                ; If A < 0 (50% chance), return from the subroutine
                        ; (as out contains an RTS)

 CPX #22                ; If X >= 22 (91% chance), return from the subroutine
 BCS out                ; (as out contains an RTS)

 LDA QQ20,X             ; If we do not have any of item QQ20+X, return from the
 BEQ out                ; subroutine (as out contains an RTS). X is in the range
                        ; 0-21, so this not only checks for cargo, but also for
                        ; E.C.M., fuel scoops, energy bomb, energy unit and
                        ; docking computer, all of which can be destroyed

 LDA DLY                ; If there is already an in-flight message on-screen,
 BNE out                ; return from the subroutine (as out contains an RTS)

 LDY #3                 ; Set bit 1 of de, the equipment destruction flag, so
 STY de                 ; that when we call MESS below, " DESTROYED" is appended
                        ; to the in-flight message

 STA QQ20,X             ; A is 0 (as we didn't branch with the BNE above), so
                        ; this sets QQ20+X to 0, which destroys any cargo or
                        ; equipment we have of that type

 CPX #17                ; If X >= 17 then we just lost a piece of equipment, so
 BCS ou1                ; jump to ou1 to print the relevant message

 TXA                    ; Print recursive token 48 + A as an in-flight token,
 ADC #208               ; which will be in the range 48 ("FOOD") to 64 ("ALIEN
 JMP MESS               ; ITEMS") as the C flag is clear, so this prints the
                        ; destroyed item's name, followed by " DESTROYED" (as we
                        ; set bit 1 of the de flag above), and returns from the
                        ; subroutine using a tail call

.ou1

 BEQ ou2                ; If X = 17, jump to ou2 to print "E.C.M.SYSTEM
                        ; DESTROYED" and return from the subroutine using a tail
                        ; call

 CPX #18                ; If X = 18, jump to ou3 to print "FUEL SCOOPS
 BEQ ou3                ; DESTROYED" and return from the subroutine using a tail
                        ; call

 TXA                    ; Otherwise X is in the range 19 to 21 and the C flag is
 ADC #113-20            ; set (as we got here via a BCS to ou1), so we set A as
                        ; follows:
                        ;
                        ;   A = 113 - 20 + X + C
                        ;     = 113 - 19 + X
                        ;     = 113 to 115

 JMP MESS               ; Print recursive token A ("ENERGY BOMB", "ENERGY UNIT"
                        ; or "DOCKING COMPUTERS") as an in-flight message,
                        ; followed by " DESTROYED", and return from the
                        ; subroutine using a tail call