I managed to get the fuel part working (from a fuel pipe running underneath it). Here's the init.lua: default.furnace_inactive_formspec = "invsize[8,9;]".. "image[2,2;1,1;default_furnace_fire_bg.png]".. "list[current_name;fuel;2,3;1,1;]".. "list[current_name;src;2,1;1,1;]".. "list[current_name;dst;5...