wither builder

local dt = tonumber(arg[1]) or 12

local ws = "minecraft:skull"
local ss = "minecraft:soul_sand"
local infront = turtle.place


local function rep(f,n)
    n = n or 1
    for i=1, n do
        turtle[f]()
    end
end

local function placeBlock(b,f)
    f = f or infront
    local s = turtle.getSelectedSlot()
    for i=1, 16 do
        local item = turtle.getItemDetails()
        if item and item.name == b then
            f()
            return
        end
        s = (s%16)+1
        turtle.select(s)
    end
    error("block "..b.." not found")
end


while true do
    rep("forward",5)
    placeBlock(ss)
    rep("turnLeft")
    placeBlock(ss)
    rep("turnRight",2)
    placeBlock(ss)
    rep("turnLeft")
    rep("back")
    placeBlock(ss)
    rep("turnLeft")
    placeBlock(ws)
    rep("turnRight",2)
    placeBlock(ws)
    rep("turnLeft")
    rep("back")
    placeBlock("ws")
    rep("back",3)

    sleep(dt)
end