Furnace recipes work in crafting interfaces and interfere with crafting recipes

• Logs placed in the top-left crafting grid slot give charcoal as ouput
• The furnace crafting recipe will give one stone as output
• In general, any smeltable item placed in the top-left slot is crafted into its smelted version (sand -> glass, etc), regardless of items placed in the other 3 (or 8) crafting slots