builder

--Variables
length = 6 --The length of the inner area of the arena, only even numbers.
side = "right" --Leave this alone.
rows = 3 --Use half the rows, can only handle whole numbers.

--Functions
function start() -- Controlling the movement and places blocks.
   for i = 1,rows do
     place()
     move()
     navigateRight()
     place()
     move()
     navigateLeft()
   end
end

function home() -- Sends the turtle home, must be used after start() is done.
     turtle.turnLeft()
     turtle.forward()
     turtle.forward()
     turtle.forward()
     turtle.forward()
     turtle.forward()
     turtle.forward()
     turtle.turnRight()
     turtle.back()
end

function navigateRight() -- Handles the turtles navigation to the right.
    turtle.turnRight()
    turtle.forward()
    turtle.turnRight()
    place()
end

function navigateLeft() -- Handles the turtles navigation to the left.
    turtle.turnLeft()
    turtle.forward()
    turtle.turnLeft()
    place()
end

function move() -- Places a block and then moves the turtle forward.
   for i = 1,length do
    place()
    turtle.forward()
   end
end

function place() -- Handles the placement of blocks.
    if turtle.detectUp() == false then
       turtle.placeUp()
    else
       turtle.forward()
    end
end

-- Code to be executed
start()
home()