So I tried my hand at writing a water-physics/fluid-dynamics system for Project Zomboid.
The result isn’t quite what I expected:
Fire poses a real threat to your survival in the game, as you could spend ages barricading your chosen safe-house, and stocking it with precious salvaged supplies, then have the whole thing go up in smoke after miss-throwing a home-made Molotov cocktail or some other crafted incendiary device. Another scenario could be a zombie knocking over a brazier near your current lodgings.
The fire is designed to spread in organic/non-predictable ways, rather than simply spread out in a ring. This is to add an extra challenge to getting the thing extinguished before it ruins all of your hard work.
Plus it looks really cool!