Still cranking and squashing

Squashed another handful of bugs in the guard code, but still not done!

Discovered in the process that the player movement code also had a bug; the rendering looked fine on the screen but it didn't update one of the 'logical playfields' correctly - effectively leaving a clone of the player on top of every ladder they've climbed. Made it somewhat easier for the guards to kill the player!

I've deduced that the unknown guard state variable is, in a nutshell, the state of the guard. I'm yet to work out the meaning of all the different values, but 7-12 mean that the guard is wriggling to get out of a hole and - I think - negative means he's carrying gold!?! There's a bit more to it, too.

The guard state is also influenced by other variables, including an initialiser in the main game loop that takes into account the total number of guards on the level, amongst other things. A look-up table is then used to calculate the actual initial value. This is unexpectedly complicating matters somewhat, as the 'wrong' initialiser value causes guards to behave improperly.

Anyway, the guards all run left (and fall) properly now (except for a graphics glitch after the very first frame of gameplay), but are yet to be killed by the holes filling in. That I'll be implementing next session, and will hopefully shed further light on the guard status byte.

Still plenty to do, I'm afraid.