Upgrade Levels

Level	Name	Required Material	Quantity
0	No Upgrade	N/A	0
1	Iron Furnace	Iron Ingot	16
2	Gold Furnace	Gold Ingot	32
3	Emerald Furnace	Emerald	16
4	Diamond Furnace	Diamond	16
5	Netherite Furnace	Netherite Ingot	8

• Level 0 (No Upgrade): Standard furnace behavior.

• Levels 1-5: Each level increases smelting speed and fuel consumption.