.TT100 LDA nmiTimerLo ; Store the low byte of the NMI timer (which will be STA RAND ; pretty random) in the RAND seed LDA K%+6 ; Store the z_lo coordinate for the planet (which will STA RAND+1 ; be pretty random) in the RAND+1 seed LDA soundVibrato ; Store the soundVibrato variable (which will be pretty STA RAND+3 ; random) in the RAND+3 seed LDA QQ12 ; Fetch the docked flag from QQ12 into A BEQ game2 ; If we are docked, jump down to MLOOP to skip all the JMP MLOOP ; the flight and spawning code in the top part of the ; main loop .game2 JSR M% ; Call M% to iterate through the main flight loop DEC MCNT ; Decrement the main loop counter in MCNT BEQ P%+5 ; If the counter has reached zero, which it will do ; every 256 main loops, skip the next JMP instruction ; (or to put it another way, if the counter hasn't ; reached zero, jump down to MLOOP, skipping all the ; following checks) .ytq JMP MLOOP ; Jump down to MLOOP to do some end-of-loop tidying and ; restart the main loop ; We only get here once every 256 iterations of the ; main loop. If we aren't in witchspace and don't ; already have 3 or more asteroids in our local bubble, ; then this section has a 13% chance of spawning ; something benign (the other 87% of the time we jump ; down to consider spawning cops, pirates and bounty ; hunters) ; ; If we are in that 13%, then 50% of the time this will ; be a Cobra Mk III trader, and the other 50% of the ; time it will either be an asteroid (98.5% chance) or, ; very rarely, a cargo canister (1.5% chance) LDA MJ ; If we are in witchspace (in which case MJ > 0) or ORA demoInProgress ; demoInProgress > 0 (in which case we are playing the BNE ytq ; demo), jump down to MLOOP (via ytq above) JSR DORND ; Set A and X to random numbers CMP #40 ; If A >= 40 (85% chance), jump down to MTT1 to skip BCS MTT1 ; the spawning of an asteroid or cargo canister and ; potentially spawn something else LDA JUNK ; If we already have 3 or more bits of junk in the local CMP #3 ; bubble, jump down to MTT1 to skip the following and BCS MTT1 ; potentially spawn something else JSR ZINF ; Call ZINF to reset the INWK ship workspace LDA #38 ; Set z_hi = 38 (far away) STA INWK+7 JSR DORND ; Set A, X and C flag to random numbers STA INWK ; Set x_lo = random STX INWK+3 ; Set y_lo = random ; ; Note that because we use 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 AND #%10000000 ; Set x_sign = bit 7 of x_lo STA INWK+2 TXA ; Set y_sign = bit 7 of y_lo AND #%10000000 STA INWK+5 ROL INWK+1 ; Set bit 1 of x_hi to the C flag, which is random, so ROL INWK+1 ; this randomly moves us off-centre by 512 (as if x_hi ; is %00000010, then (x_hi x_lo) is 512 + x_lo) JSR DORND ; Set A, X and V flag to random numbers AND #%00110000 ; If either of bits 4 and 5 are set (75% chance), skip BNE P%+5 ; the following instruction JMP MTT4 ; Jump up to MTT4 to spawn a trader (25% chance) ORA #%01101111 ; Take the random number in A and set bits 0-3 and 5-6, STA INWK+29 ; so the result has a 50% chance of being positive or ; negative, and a 50% chance of bits 0-6 being 127. ; Storing this number in the roll counter therefore ; gives our new ship a fast roll speed with a 50% ; chance of having no damping, plus a 50% chance of ; rolling clockwise or anti-clockwise LDA SSPR ; If we are inside the space station safe zone, jump BNE MLOOPS ; down to MLOOPS to stop spawning TXA ; Set A to the random X we set above, which we haven't BCS MTT2 ; used yet, and if the C flag is set (50% chance) jump ; down to MTT2 to skip the following AND #31 ; Set the ship speed to our random number, reduced to ORA #16 ; the range 16 to 31 STA INWK+27 BCC MTT3 ; Jump down to MTT3, skipping the following (this BCC ; is effectively a JMP as we know the C flag is clear, ; having passed through the BCS above) .MTT2 ORA #%01111111 ; Set bits 0-6 of A to 127, leaving bit 7 as random, so STA INWK+30 ; storing this number in the pitch counter means we have ; full pitch with no damping, with a 50% chance of ; pitching up or down .MTT3 JSR DORND ; Set A and X to random numbers CMP #252 ; If random A < 252 (98.8% of the time), jump to thongs BCC thongs ; to skip the following LDA #HER ; Set A to #HER so we spawn a rock hermit 1.2% of the ; time STA INWK+32 ; Set byte #32 to %00001111 to give the rock hermit an ; E.C.M. BNE whips ; Jump to whips (this BNE is effectively a JMP as A will ; never be zero) .thongs CMP #10 ; If random A >= 10 (96% of the time), set the C flag AND #1 ; Reduce A to a random number that's 0 or 1 ADC #OIL ; Set A = #OIL + A + C, so there's a tiny chance of us ; spawning a cargo canister (#OIL) and an even chance of ; us spawning either a boulder (#OIL + 1) or an asteroid ; (#OIL + 2) .whips JSR NWSHP ; Add our new asteroid or canister to the universeName: Main game loop (Part 2 of 6) [Show more] Type: Subroutine Category: Main loop Summary: Call the main flight loop, and potentially spawn a trader, an asteroid, or a cargo canister 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 6 of 6) calls via TT100
This section covers the following: * Call M% to do the main flight loop * Potentially spawn a trader, asteroid or cargo canister
Other entry points: TT100 The entry point for the start of the main game loop, which calls the main flight loop and the moves into the spawning routine
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Subroutine DORND (category: Maths (Arithmetic))
Generate random numbers
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Configuration variable HER = 15
Ship type for a rock hermit (asteroid)
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Workspace K% (category: Workspaces)
Ship data blocks
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Entry point M% in subroutine Main flight loop (Part 1 of 16) (category: Main loop)
The entry point for the main flight loop
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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 MTT1 in subroutine Main game loop (Part 3 of 6)
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Label MTT2 is local to this routine
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Label MTT3 is local to this routine
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Label MTT4 in subroutine Main game loop (Part 1 of 6)
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Subroutine NWSHP (category: Universe)
Add a new ship to our local bubble of universe
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Configuration variable OIL = 5
Ship type for a cargo canister
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Subroutine ZINF (category: Universe)
Reset the INWK workspace and orientation vectors
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Variable demoInProgress in workspace WP
A flag to determine whether we are playing the demo
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Label game2 is local to this routine
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Variable nmiTimerLo in workspace ZP
Low byte of a counter that's incremented by 1 every time nmiTimer wraps
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Variable soundVibrato in workspace WP
The four-byte seeds for adding randomised vibrato to the current sound effect
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Label thongs is local to this routine
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Label whips is local to this routine
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Label ytq is local to this routine