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BBC Micro Elite

Flight: OUCH

Name: OUCH [View in context] Type: Subroutine Category: Flight Summary: Potentially lose cargo or equipment following damage
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 (89% 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 BNE 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 BNE 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