make it so grass blocks will turn into dirt blocks when set on fire

but only when the grass blocks are directly set on fire. They still wouldn’t spread fire, since that would just turn the overworld into Australia, and nobody wants that

Updated version:

I’m adding some new details from the comments’ ideas, as well as some of my own input.

I’m changing the original idea of grass turning into dirt when burned. It should actually become a new block, Scorched Grass.

Scorched Grass cannot turn back into regular grass. It can be picked up with silk touch, and if you pick it up without silk touch, it turns into regular dirt. And once you place the dirt back down, it will eventually become grass again.

Also, in the Savannah biome, fires can spread on grass for up to ten blocks in every direction on the same level, due to the grass being drier. It can spread about the same speed as leaves.

Any grass that somehow ends up in a desert or badlands biome will have the same effect, due to those areas being dry.

Grass in other biomes will not spread due to the grass being moist (or if it does spread, then only about 3 blocks on the same level in every direction at most)