I don't think #2041 should affect this. Carpets are a thin layer at the bottom of their cell, so you can detect when an entity enters that cell with onEntityInside(). #2041 only affects full-blocks which need to be collidable.

I think this seems to be something missing in pocketmine, Slime block should also not deal damage if there is carpet on top of it. Jumping on a Carpet can also damage Farmland and on Beds it also gives a bouncing effect if they are under it.
Do we need to create an onEntityLand function on the carpet that calls onEntityLand on the block below it?

I think this seems to be something missing in pocketmine, Slime block should also not deal damage if there is carpet on top of it. Jumping on a Carpet can also damage Farmland and on Beds it also gives a bouncing effect if they are under it. Do we need to create an onEntityLand function on the carpet that calls onEntityLand on the block below it?

Hmm, not sure. Maybe leave that out of this PR then.

I'm not very clear how powder snow is supposed to work. Are there any non-mobs affected by it? It seems weird to me that general entities should be affected.

Freezing a burning entity should extinguish its fire, such as an arrow fired with the flame enchantment. However, we handle it in the PowderSnow block here.
Should we just move the freeze codes to Living?

Yeah, I think so. Unless there are any non-living entities that can have the freeze effects.

I've attached a plugin to the test section for plugin developers who want to try it out, in case they want to create a troll plugin or custom enchant. Any suggestions would be helpful.

This looks good now. Will test soon and feedback

Looks like we have a simulation issue with the collision boxes. Since the collision AABB is different if the entity is wearing leather boots or not (they should be able to stand on the powder snow). For non player entities I don't think this will work currently.

I'm not too sure how that should be addressed though, since we don't really have the systems to deal with that...

Hmm... Some mobs like foxes can also stand on powder snow (unless it does a jumping attack on a chicken in the powder snow). This might be a problem if we want to implement Scaffolding block. I think the collision is just as complex because it only prevents falling, but allows for passing from the side.
Should we enforce the collision as a full block for now?

No, that would prevent regular mobs from falling inside it.

This needs to be fixed properly with a more general solution. I have a rough idea how to deal with it, but collision detection is very performance-sensitive code, so it needs to be handled carefully.