DEC EV \ Decrement EV, the extra vessels spawning delay, and if BPL MLOOPS \ it is still positive, jump to MLOOPS to stop spawning, \ so we only do the following when the EV counter runs \ down INC EV \ EV is negative, so bump it up again, setting it back \ to 0 LDA TP \ Fetch bits 2 and 3 of TP, which contain the status of AND #%00001100 \ mission 2 CMP #%00001000 \ If bit 3 is set and bit 2 is clear, keep going to BNE nopl \ spawn a Thargoid as we are transporting the plans in \ mission 2 and the Thargoids are trying to stop us, \ otherwise jump to nopl to skip spawning a Thargoid JSR DORND \ Set A and X to random numbers CMP #200 \ If the random number in A < 200 (78% chance), jump to BCC nopl \ nopl to skip spawning a Thargoid .fothg2 JSR GTHG \ Call GTHG to spawn a Thargoid ship and a Thargon \ companion .nopl JSR DORND \ Set A and X to random numbers LDY gov \ If the government of this system is 0 (anarchy), jump BEQ LABEL_2 \ straight to LABEL_2 to start spawning pirates or \ bounty hunters CMP #120 \ If the random number in A >= 120 (53% chance), jump to BCS MLOOPS \ MLOOPS to stop spawning (so there's a 47% chance of \ spawning pirates or bounty hunters) AND #7 \ Reduce the random number in A to the range 0-7, and CMP gov \ if A is less than government of this system, jump BCC MLOOPS \ to MLOOPS to stop spawning (so safer governments with \ larger gov numbers have a greater chance of jumping \ out, which is another way of saying that more \ dangerous systems spawn pirates and bounty hunters \ more often) .LABEL_2 \ --- Mod: Code removed for Elite-A: ------------------> \ \ Now to spawn a lone bounty hunter or a group of \ \ pirates \ \ JSR Ze \ Call Ze to initialise INWK to a potentially hostile \ \ ship, and set A and X to random values \ \ \ \ Note that because Ze uses the value of X returned by \ \ DORND, and X contains the value of A returned by the \ \ previous call to DORND, this does not set the new ship \ \ to a totally random location. See the deep dive on \ \ "Fixing ship positions" for details \ \ CMP #100 \ If the random number in A >= 100 (61% chance), jump \ BCS mt1 \ to mt1 to spawn pirates, otherwise keep going to \ \ spawn a lone bounty hunter \ --- And replaced by: --------------------------------> \ Now to spawn a group of bounty hunters, a Thargoid or \ a pack of pirates CPX #100 \ If the random number in X >= 100 (61% chance), jump BCS mt1 \ to mt1 to spawn pirates, otherwise keep going to \ spawn bounty hunters or a Thargoid \ --- End of replacement ------------------------------> INC EV \ Increase the extra vessels spawning counter, to \ prevent the next attempt to spawn extra vessels AND #3 \ Set A = random number in the range 0-3, which we \ will now use to determine the type of ship \ --- Mod: Code removed for Elite-A: ------------------> \ ADC #CYL2 \ Add A to #CYL2 (we know the C flag is clear as we \ \ passed through the BCS above), so A is now one of the \ \ lone bounty hunter ships, i.e. Cobra Mk III (pirate), \ \ Asp Mk II, Python (pirate) or Fer-de-lance \ \ \ \ Interestingly, this logic means that the Moray, which \ \ is the ship after the Fer-de-lance in the XX21 table, \ \ never spawns, as the above logic chooses a blueprint \ \ number in the range CYL2 to CYL2+3 (i.e. 24 to 27), \ \ and the Moray is blueprint 28 \ \ \ \ No other code spawns the ship with blueprint 28, so \ \ this means the Moray is never seen in Elite \ \ \ \ This is presumably a bug, which could be very easily \ \ fixed by inserting one of the following instructions \ \ before the ADC #CYL2 instruction above: \ \ \ \ * SEC would change the range to 25 to 28, which \ \ would cover the Asp Mk II, Python (pirate), \ \ Fer-de-lance and Moray \ \ \ \ * LSR A would set the C flag to a random number to \ \ give a range of 24 to 28, which would cover the \ \ Cobra Mk III (pirate), Asp Mk II, Python (pirate), \ \ Fer-de-lance and Moray \ \ \ \ It's hard to know what the authors' original intent \ \ was, but the second approach makes the Moray and Cobra \ \ Mk III the rarest choices, with the Asp Mk II, Python \ \ and Fer-de-Lance being more likely, and as the Moray \ \ is described in the literature as a rare ship, and the \ \ Cobra can already be spawned as part of a group of \ \ pirates (see mt1 below), I tend to favour the LSR A \ \ solution over the SEC approach \ --- And replaced by: --------------------------------> ADC #25 \ Add A to 25 (we know the C flag is clear as we passed \ through the BCS above), so A is now a ship blueprint \ position in the range 25-28, which is where the bounty \ hunter ships live in the ship files \ --- End of replacement ------------------------------> TAY \ Copy the new ship type to Y JSR THERE \ Call THERE to see if we are in the Constrictor's \ system in mission 1 BCC NOCON \ If the C flag is clear then we are not in the \ Constrictor's system, so skip to NOCON LDA #%11111001 \ Set the AI flag of this ship so that it has E.C.M., STA INWK+32 \ has a very high aggression level of 28 out of 31, is \ hostile, and has AI enabled - nasty stuff! LDA TP \ Fetch bits 0 and 1 of TP, which contain the status of AND #%00000011 \ mission 1 LSR A \ Shift bit 0 into the C flag BCC NOCON \ If bit 0 is clear, skip to NOCON as mission 1 is not \ in progress ORA MANY+CON \ Bit 0 of A now contains bit 1 of TP, so this will be \ set if we have already completed mission 1, so this OR \ will be non-zero if we have either completed mission \ 1, or there is already a Constrictor in our local \ bubble of universe (in which case MANY+CON will be \ non-zero) BEQ YESCON \ If A = 0 then mission 1 is in progress, we haven't \ completed it yet, and there is no Constrictor in the \ vicinity, so jump to YESCON to spawn the Constrictor .NOCON TYA \ Set A to the new ship type in Y EQUB &2C \ Skip the next instruction by turning it into \ &2C &A9 &1F, or BIT &1FA9, which does nothing apart \ from affect the flags .YESCON LDA #CON \ If we jump straight here, we are in the mission 1 \ endgame and it's time to spawn the Constrictor, so \ set A to the Constrictor's type .focoug JSR NWSHP \ Spawn the new ship, whether it's a pirate or \ Constrictor .mj1 JMP MLOOP \ Jump down to MLOOP, as we are done spawning ships .mt1 \ --- Mod: Code removed for Elite-A: ------------------> \ AND #3 \ It's time to spawn a group of pirates, so set A to a \ \ random number in the range 0-3, which will be the \ \ loop counter for spawning pirates below (so we will \ \ spawn 1-4 pirates) \ \ STA EV \ Delay further spawnings by this number \ \ STA XX13 \ Store the number in XX13, the pirate counter \ \.mt3 \ \ JSR DORND \ Set A and X to random numbers \ \ STA T \ Set T to a random number \ \ JSR DORND \ Set A and X to random numbers \ \ AND T \ Set A to the AND of two random numbers, so each bit \ \ has 25% chance of being set which makes the chances \ \ of a smaller number higher \ \ AND #7 \ Reduce A to a random number in the range 0-7, though \ \ with a bigger chance of a smaller number in this range \ \ STA CPIR \ Set CPIR to this random number in the range 0-7 \ \.more \ \ LDA CPIR \ Set A to the ship type in CPIR \ \ ADC #PACK \ #PACK is set to #SH3, the ship type for a Sidewinder, \ \ so this sets our new ship type to one of the pack \ \ hunters, namely a Sidewinder, Mamba, Krait, Adder, \ \ Gecko, Cobra Mk I, Worm or Cobra Mk III (pirate) \ --- And replaced by: --------------------------------> LDA #17 \ Fall through into hordes to spawn a pack of ships from LDX #7 \ ship blueprint positions 17 to 24, which is where the \ pirate ships live in the ship blueprint files .hordes \ This routine spawns a pack of ships, made up of ships \ from type A to type A + X, with the pack size normally \ being one to four ships, but rarely being up to eight \ ships \ \ Let's call A the "base ship type", and X the "ship \ type range" STA horde_base+1 \ Modify the ADC instruction at horde_base so that it \ adds the base ship type given in A STX horde_mask+1 \ Modify the ADC instruction at horde_mask so that it \ ANDs the ship type range given in X JSR DORND \ Set A and X to random numbers CMP #248 \ If A >= 248 (3.1% chance), jump to horde_large so we BCS horde_large \ potentially spawn a larger pack (i.e. up to 8 ships) STA XX13 \ We are going to spawn a smaller pack (i.e. up to 4 TXA \ ships), so set: AND XX13 \ AND #3 \ A = A AND X AND 3 \ \ to give a random pack size of 0-3, with a greater \ chance of the smaller numbers than the larger ones \ (due to the AND). This will be our pack size, which \ won't be affected further by the following AND \ instruction .horde_large AND #7 \ If we are going to spawn a larger pack, reduce the \ random number in A to the range 0-7, with an equal \ chance of each of the numbers. This will be our pack \ size \ By this point our pack size is in A, and is either \ 0-3 or 0-7 STA EV \ Delay further spawnings by this number STA XX13 \ Store the number in XX13, the pack size counter .mt3 JSR DORND \ Set A and X to random numbers STA T \ Set A = A AND X TXA \ AND T \ which is in the range 0-255, but with a greater chance \ of being a smaller number (due to the AND) .horde_mask AND #&FF \ This instruction gets modified so that it ANDs the \ ship type range given in the argument X to the \ hordes routine, i.e. it turns into AND #type_range, \ which reduces our random number to be between 0 and \ the ship type range (so if we add this number to the \ base ship type, it will pick a random ship type from \ within the range A to A + X, where A and X are the \ arguments to the original call to hordes STA CPIR \ Set CPIR to our random number in the range 0 to \ the ship type .more LDA CPIR \ Set A to the ship type in CPIR CLC \ Clear the C flag for the addition below .horde_base ADC #0 \ This instruction gets modified so that it adds the \ ship type given in the argument A to the hordes \ routine, i.e. it turns into ADC #ship_type, so this \ sets A to a ship type in the range we want INC INWK+27 \ Increment the speed of the ship we are about to spawn, \ so later ships in the pack go faster INC INWK+1 \ Increment the x_hi coordinate of the ship we are about \ to spawn, so later ships in the pack are spread out to \ the sides INC INWK+4 \ Increment the y_hi coordinate of the ship we are about \ to spawn, so later ships in the pack are spread out \ to the top and bottom \ --- End of replacement ------------------------------> JSR NWSHP \ Try adding a new ship of type A to the local bubble \ --- Mod: Code removed for Elite-A: ------------------> \ BCS P%+7 \ If the ship was successfully added, skip the following \ \ two instructions \ \ DEC CPIR \ The ship wasn't added, which might be because the ship \ \ blueprint for this ship type isn't in the currently \ \ loaded ship blueprints file, so decrement CPIR to \ \ point to the previous ship type, so we can try \ \ spawning that type of pirate instead \ \ BPL more \ Loop back to more to have another go at spawning this \ \ pirate, until we have tried spawning a Sidewinder when \ \ CPIR is 0, in which case give up and move on to the \ \ next pirate to spawn \ \ DEC XX13 \ Decrement the pirate counter \ \ BPL mt3 \ If we need more pirates, loop back up to mt3, \ \ otherwise we are done spawning, so fall through into \ \ the end of the main loop at MLOOP \ --- And replaced by: --------------------------------> CMP #24 \ This compares the value of A (which is set to the \ x_sign value of the spawned ship by NWSHP), but the \ result isn't used anywhere, as CMP affects the Z and N \ flags (not the C flag), and these same flags will be \ overwritten by the two DEC instructions below... so \ this instruction has no effect BCS P%+7 \ If the ship was successfully added, skip the following \ two instructions DEC CPIR \ The ship wasn't added, which might be because the ship \ blueprint for this ship type isn't in the currently \ loaded ship blueprints file, so decrement CPIR to \ point to the previous ship type, so we can try \ spawning that type of ship instead BPL more \ Loop back to more to have another go at spawning this \ ship, until CPIR is 0, in which case we have tried \ spawning all the ship types in the range, so give up \ and move on to the next pirate to spawn DEC XX13 \ Decrement the pack size counter BPL mt3 \ If we need more ships, loop back up to mt3, \ otherwise we are done spawning, so fall through into \ the end of the main loop at MLOOP \ --- End of replacement ------------------------------>Name: Main game loop (Part 4 of 6) [Show more] Type: Subroutine Category: Main loop Summary: Potentially spawn a lone bounty hunter or up to four pirates Deep dive: Program flow of the main game loop Ship data blocks Fixing ship positionsContext: See this subroutine in context in the source code References: This subroutine is called as follows: * Main game loop (Part 1 of 6) calls via hordes * Main game loop (Part 3 of 6) calls via hordes
This section covers the following: * Potentially spawn (47% chance) either a pack of up to 8 bounty hunters, or a pack of up to 8 pirates * Also potentially spawn a Constrictor if this is the mission 1 endgame, or Thargoids if mission 2 is in progress
Other entry points: hordes Spawn a pack of ships, made up of ships from type A to type A + X, with the pack size normally being one to four ships, but rarely being up to eight ships
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Configuration variable CON = 31
Ship blueprint position for the Constrictor
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Subroutine DORND (category: Maths (Arithmetic))
Generate random numbers
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Subroutine GTHG (category: Universe)
Spawn a Thargoid ship and a Thargon companion
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Label LABEL_2 is local to this routine
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Entry point MLOOP in subroutine Main game loop (Part 5 of 6) (category: Main loop)
The entry point for the main game loop. This entry point comes after the call to the main flight loop and spawning routines, so it marks the start of the main game loop for when we are docked (as we don't need to call the main flight loop or spawning routines if we aren't in space)
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Label MLOOPS in subroutine Main game loop (Part 3 of 6)
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Label NOCON is local to this routine
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Subroutine NWSHP (category: Universe)
Add a new ship to our local bubble of universe
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Subroutine THERE (category: Missions)
Check whether we are in the Constrictor's system in mission 1
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Label YESCON is local to this routine
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Label horde_base is local to this routine
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Label horde_large is local to this routine
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Label horde_mask is local to this routine
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Label more is local to this routine
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Label mt1 is local to this routine
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Label mt3 is local to this routine
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Label nopl is local to this routine