blockgame/mods/bg_stoneworking/recipe.lua

local modname = minetest.get_current_modname()

local function is_stoney_below (pos)
	local below_node = minetest.get_node(pos + blockgame.vector.dirs.down)
	return blockgame.item_matches(below_node.name, {"group:stoney"})
end

blockgame.crafting.register_pummel_recipe({
	name = modname .. ":craft_tile",
	label = "pummel stone into tile",
	used = {"group:stoney"},
	target = {"bg_terrain:cobblestone"},
	check = function (pos, used_node, target_node)
		return is_stoney_below(pos)
	end,
	on_success = function (pos, used_node, target_node)
		minetest.set_node(pos, {name = modname .. ":tile"})
	end,
})

blockgame.crafting.register_pummel_recipe({
	name = modname .. ":craft_bricks",
	label = "pummel tile into bricks",
	used = {"group:stoney"},
	target = {modname .. ":tile"},
	check = function (pos, used_node, target_node)
		return is_stoney_below(pos)
	end,
	on_success = function (pos, used_node, target_node)
		minetest.set_node(pos, {name = modname .. ":bricks"})
	end,
})

local crush_recipes = {
	{
		input = {"bg_terrain:cobblestone", "bg_terrain:cobblestone_loose"},
		output = modname .. ":tile",
	},
	{
		input = {modname .. ":tile"},
		output = modname .. ":bricks",
	},
}

blockgame.register_after_falling_node_lands(function (pos, node, entity)
	if not blockgame.item_matches(node.name, {"group:stoney"}) then return end

	local def = minetest.registered_nodes[node.name]
	local mass = def.mass or 1
	local force = math.abs(entity.fall_velocity.y) * mass

	if force < 5 then return end

	local below = pos + blockgame.vector.dirs.down
	local target = minetest.get_node(below).name
	if not blockgame.item_matches(target, {"group:stoney"}) then return end

	for _, recipe in pairs(crush_recipes) do
		local input = recipe.input
		local output = recipe.output
		if blockgame.item_matches(target, input) then
			minetest.set_node(below, {name = output})
			return
		end
	end
end)