bridge.lua

local component = require("component")
local robot = component.proxy(component.list("robot")() or error("No robot component"))
local sides = require("sides")

local length = 10
local width = 3

function move(right)
  robot.turn(right)
  robot.move(sides.front)
  robot.turn(not right)
  robot.move(sides.back)
end

function select(direction)
  while not robot.compare(sides.down) do
    robot.select(robot.select() % robot.inventorySize() + direction)
  end
end

function start()
  right = true
  direction = 1
  for y = 1, length-1 do
    for x = 1, width do
      select(direction)
      robot.move(sides.front)
      robot.place(sides.down)

      if x < width then
        move(right)
      end
    end
    right = not right
    direction = -direction
  end
end