areaYSize = 3*5
areaXSize = 3*5
areaZSize = 20
forward = true

for z=1,areaZSize do
    for y=1,areaYSize do
        for x=1,areaXSize do
            turtle.dig()
            if not turtle.forward() then
                turtle.refuel()
                turtle.forward()
            end
        end
        if forward then
            if not turtle.turnRight() then
                turtle.refuel()
                turtle.turnRight()
            end
            turtle.dig()
            if not turtle.forward() then
                turtle.refuel()
                turtle.forward()
            end
            if not turtle.turnRight() then
                turtle.refuel()
                turtle.turnRight()
            end
            forward = false  
        else
            if not turtle.turnLeft() then
                turtle.refuel()
                turtle.turnLeft()
            end
            turtle.dig()
            if not turtle.forward() then
                turtle.refuel()
                turtle.forward()
            end
            if not turtle.turnLeft() then
                turtle.refuel()
                turtle.turnLeft()
            end
            forward = true
        end
    end
    turtle.digUp()
    if not turtle.up() then
        turtle.refuel()
        turtle.up()
    end
    forward = not forward
end