.TA352 ; If we get here, the missile has been destroyed by ; E.C.M. or by the space station LDA INWK ; Set A = x_lo OR y_lo OR z_lo of the missile ORA INWK+3 ORA INWK+6 BNE TA872 ; If A is non-zero then the missile is not near our ; ship, so skip the next two instructions to avoid ; damaging our ship LDA #80 ; Otherwise the missile just got destroyed near us, so JSR OOPS ; call OOPS to damage the ship by 80, which is nowhere ; near as bad as the 250 damage from a missile slamming ; straight into us, but it's still pretty nasty .TA872 LDX #PLT ; Set X to the ship type for plate alloys, so we get ; awarded the kill points for the missile scraps in TA87 BNE TA353 ; Jump to TA353 to process the missile kill tally and ; make an explosion sound .TA34 ; If we get here, the missile is hostile LDA #0 ; Set A to x_hi OR y_hi OR z_hi JSR MAS4 BEQ P%+5 ; If A = 0 then the missile is very close to our ship, ; so skip the following instruction JMP TN4 ; Jump down to part 3 to set up the vectors and skip ; straight to aggressive manoeuvring JSR TA873 ; The missile has hit our ship, so call TA873 to set ; bit 7 of the missile's byte #31, which marks the ; missile as being killed JSR EXNO3 ; Make the sound of the missile exploding LDA #250 ; Call OOPS to damage the ship by 250, which is a pretty JMP OOPS ; big hit, and return from the subroutine using a tail ; call .TA18 ; This is the entry point for missile tactics and is ; called from the main TACTICS routine below LDA ECMA ; If an E.C.M. is currently active (either ours or an BNE TA352 ; opponent's), jump to TA352 to destroy this missile LDA INWK+32 ; Fetch the AI flag from byte #32 and if bit 6 is set ASL A ; (i.e. missile is hostile), jump up to TA34 to check BMI TA34 ; whether the missile has hit us LSR A ; Otherwise shift A right again. We know bits 6 and 7 ; are now clear, so this leaves bits 0-5. Bits 1-5 ; contain the target's slot number, and bit 0 is cleared ; in FRMIS when a missile is launched, so A contains ; the slot number shifted left by 1 (i.e. doubled) so we ; can use it as an index for the two-byte address table ; at UNIV TAX ; Copy the address of the target ship's data block from LDA UNIV,X ; UNIV(X+1 X) to (A V) STA V LDA UNIV+1,X JSR VCSUB ; Calculate vector K3 as follows: ; ; K3(2 1 0) = (x_sign x_hi x_lo) - x-coordinate of ; target ship ; ; K3(5 4 3) = (y_sign y_hi z_lo) - y-coordinate of ; target ship ; ; K3(8 7 6) = (z_sign z_hi z_lo) - z-coordinate of ; target ship ; So K3 now contains the vector from the target ship to ; the missile LDA K3+2 ; Set A = OR of all the sign and high bytes of the ORA K3+5 ; above, clearing bit 7 (i.e. ignore the signs) ORA K3+8 AND #%01111111 ORA K3+1 ORA K3+4 ORA K3+7 BNE TA64 ; If the result is non-zero, then the missile is some ; distance from the target, so jump down to TA64 see if ; the target activates its E.C.M. LDA INWK+32 ; Fetch the AI flag from byte #32 and if only bits 7 and CMP #%10000010 ; 1 are set (AI is enabled and the target is slot 1, the BEQ TA352 ; space station), jump to TA352 to destroy this missile, ; as the space station ain't kidding around LDY #31 ; Fetch byte #31 (the exploding flag) of the target ship LDA (V),Y ; into A BIT M32+1 ; M32 contains an LDY #32 instruction, so M32+1 contains ; 32, so this instruction tests A with %00100000, which ; checks bit 5 of A (the "already exploding?" bit) BNE TA35 ; If the target ship is already exploding, jump to TA35 ; to destroy this missile ORA #%10000000 ; Otherwise set bit 7 of the target's byte #31 to mark STA (V),Y ; the ship as having been killed, so it explodes .TA35 LDA INWK ; Set A = x_lo OR y_lo OR z_lo of the missile ORA INWK+3 ORA INWK+6 BNE P%+7 ; If A is non-zero then the missile is not near our ; ship, so skip the next two instructions to avoid ; damaging our ship LDA #80 ; Otherwise the missile just got destroyed near us, so JSR OOPS ; call OOPS to damage the ship by 80, which is nowhere ; near as bad as the 250 damage from a missile slamming ; straight into us, but it's still pretty nasty .TA87 LDA INWK+32 ; Set X to bits 1-6 of the missile's AI flag in ship AND #%01111111 ; byte #32, so bits 0-4 of X are the target's slot LSR A ; number, and bit 5 is set (as the missile is hostile) TAX ; so X is fairly random and in the range 32-39 (as the ; maximum slot number is 7) LDA MJ-32,X ; Set X to entry X-32 starting from MJ table, which will TAX ; be even more random, as MJ is where we store data like ; the cabin and laser temperature ; ; The value of X is used to determine the number of kill ; points awarded for the destruction of the missile .TA353 JSR EXNO2 ; Call EXNO2 to process the fact that we have killed a ; missile (so increase the kill tally, make an explosion ; sound and so on) .TA873 ASL INWK+31 ; Set bit 7 of the missile's byte #31 flag to mark it as SEC ; having been killed, so it explodes ROR INWK+31 .TA1 RTS ; Return from the subroutine .TA64 ; If we get here then the missile has not reached the ; target JSR DORND ; Set A and X to random numbers CMP #16 ; If A >= 16 (94% chance), jump down to TA19S with the BCS TA19S ; vector from the target to the missile in K3 .M32 LDY #32 ; Fetch byte #32 for the target and shift bit 0 (E.C.M.) LDA (V),Y ; into the C flag LSR A BCS P%+5 ; If the C flag is set then the target has E.C.M. ; fitted, so skip the next instruction .TA19S JMP TA19 ; The target does not have E.C.M. fitted, so jump down ; to TA19 with the vector from the target to the missile ; in K3 JMP ECBLB2 ; The target has E.C.M., so jump to ECBLB2 to set it ; off, returning from the subroutine using a tail callName: TACTICS (Part 1 of 7) [Show more] Type: Subroutine Category: Tactics Summary: Apply tactics: Process missiles, both enemy missiles and our own Deep dive: Program flow of the tactics routineContext: See this subroutine in context in the source code References: No direct references to this subroutine in this source file
This section implements missile tactics and is entered at TA18 from the main entry point below, if the current ship is a missile. Specifically: * If E.C.M. is active, destroy the missile * If the missile is hostile towards us, then check how close it is. If it hasn't reached us, jump to part 3 so it can streak towards us, otherwise we've been hit, so process a large amount of damage to our ship * Otherwise see how close the missile is to its target. If it has not yet reached its target, give the target a chance to activate its E.C.M. if it has one, otherwise jump to TA19 with K3 set to the vector from the target to the missile * If it has reached its target and the target is the space station, destroy the missile, potentially damaging us if we are nearby * If it has reached its target and the target is a ship, destroy the missile and the ship, potentially damaging us if we are nearby
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Subroutine DORND (category: Maths (Arithmetic))
Generate random numbers
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Subroutine ECBLB2 (category: Dashboard)
Start up the E.C.M. (start the countdown and make the E.C.M. sound)
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Subroutine EXNO2 (category: Status)
Process us making a kill
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Subroutine EXNO3 (category: Sound)
Make an explosion sound
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Label M32 is local to this routine
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Subroutine MAS4 (category: Maths (Geometry))
Calculate a cap on the maximum distance to a ship
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Subroutine OOPS (category: Flight)
Take some damage
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Configuration variable PLT = 4
Ship type for an alloy plate
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Label TA19 in subroutine TACTICS (Part 3 of 7)
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Label TA19S is local to this routine
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Label TA34 is local to this routine
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Label TA35 is local to this routine
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Label TA352 is local to this routine
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Label TA353 is local to this routine
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Label TA64 is local to this routine
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Label TA872 is local to this routine
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Label TA873 is local to this routine
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Label TN4 in subroutine TACTICS (Part 3 of 7)
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Variable UNIV (category: Universe)
Table of pointers to the local universe's ship data blocks
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Subroutine VCSUB (category: Maths (Arithmetic))
Calculate vector K3(8 0) = [x y z] - coordinates in (A V)