system where blocks that are marked flammable could ignite through molotovs torches burning zombies Etc and then propagate to the block next to it depending on material and percentage so a base wood frame would have an 80% chance of igniting if the block next to it was ignited a single upgrade of wood would have a 60% chance a double upgrade of wood would have a 40% chance, the grass blocks would have a very high possibility of igniting the tree blocks and so on, you would be able to burn down buildings and clear land but also it would mean being very careful lighting things on fire in houses and tossing random molotovs during horde night.
Sides note : Flame thrower
Sides note : Flame thrower