This code appears in the following versions (click to see it in the source code):
Code variations between these versions are shown below.
Name: Main game loop (Part 1 of 6) Type: Subroutine Category: Main loop
Deep dive: Program flow of the main game loop Ship data blocks Aggression and hostility in ship tactics
This is part of the main game loop. This is where the core loop of the game lives, and it's in two parts. The shorter loop (just parts 5 and 6) is iterated when we are docked, while the entire loop from part 1 to 6 iterates if we are in space. This section covers the following:
.MTT4
JSR DORND \ Set A and X to random numbers
LSR A \ Clear bit 7 of our random number in A and set the C \ flag to bit 0 of A, which is random STA INWK+32 \ Store this in the ship's AI flag, so this ship does \ not have AI STA INWK+29 \ Store A in the ship's roll counter, giving it a \ clockwise roll (as bit 7 is clear), and a 1 in 127 \ chance of it having no damping ROL INWK+31 \ This instruction would appear to set bit 0 of the \ ship's missile count randomly (as the C flag was set), \ giving the ship either no missiles or one missile \ \ However, INWK+31 is overwritten in the call to the \ NWSHP routine below, where it is set to the number of \ missiles from the ship blueprint, and the value of the \ C flag is not used, so this instruction actually has \ no effect \ \ Interestingly, the original source code for the NWSPS \ routine also has an instruction that sets INWK+31 and \ which gets overwritten when it falls through into \ NWSHP, but in this case the instruction is commented \ out in the source. Perhaps the original version of \ NWSHP didn't set the missile count and instead relied \ on the calling code to set it, and when the authors \ changed it, they commented out the INWK+31 instruction \ in NWSPS and forgot about this one. Who knows?
Traders in the enhanced versions can spawn in docking mode, in which case they mind their own business.
This variation is blank in the Cassette and Electron versions.
JSR DORND \ Set A and X to random numbers, plus the C flag BMI nodo \ If A is negative (50% chance), jump to nodo to skip \ the following \ If we get here then we are going to spawn a ship that \ is minding its own business and trying to dock LDA INWK+32 \ Set bits 6 and 7 of A, so the ship has AI (bit 7) and ORA #%11000000 \ an aggression level of at least 32 out of 63 (this STA INWK+32 \ makes the ship more likely to turn towards its target, \ which in this case is the space station, as we are \ about to set the ship flags so it is docking) LDX #%00010000 \ Set bit 4 of the ship's NEWB flags, to indicate that STX NEWB \ this ship is docking .nodo
Traders in the enhanced versions can be one of the following: Cobra Mk III, Python, Boa or Anaconda (in the cassette and Electron versions, they are always Cobras).
Tap on a block to expand it, and tap it again to revert.
The advanced versions have rock hermits, which are classed as junk but can release ships if attacked.
This variation is blank in the Cassette, Disc (flight) and Electron versions.
CMP #HER \ If A is now the ship type of a rock hermit, jump to BEQ TT100 \ TT100 to skip the following instruction