Simple Strip mine BETA

--[[
        ** Simple StripMine BETA**
        ** Written by: TheSwiftVlogger **
        Warning: Bugs and errors are still occurring

        *CHANGE LOG*

        version 0.0.1:
            - System booting intro added
            - added fuel check

        version 0.1.0
            - Bug fixes
            - added sand/gravel protection

        version 0.1.10
            - Complete re-written and restructured code

        Current bugs
            - torches not placing


]]--

local sd = "Place fuel in slot 1, torches in slot 2"
local ss = "Welcome, booting system, please hold.."
local ld = "Loading required drivers"
local cf = "Checking fuel levels."
local fr = "Fuel remaining: "
local gf = turtle.getFuelLevel()
local pe = "press <Enter> to continue"

function intro()    --simple cosmetic intro
term.clear()
term.setCursorPos(1, 1)
print(sd)
sleep(1)
term.setCursorPos(5, 7)
print(pe)
    x = read()
term.clear()
term.setCursorPos(1, 1)
    print(ss)
        sleep(3)
term.setCursorPos(1, 2)
    print(cf)
        sleep(1.2)
term.setCursorPos(1, 3)
    print(fr.." "..gf)
        sleep(1)
term.setCursorPos(5, 7)
    print(pe)
    x = read()
term.clear()
term.setCursorPos(1, 1)
end

local ac = "How Long to mine? "     -- not function yet*

function input()
       --for future plans*
end

function cFuel()            --check fuel level, if below 30 will automatically refuel
    if turtle.getFuelLevel() < 29 then
        turtle.refuel(1)
    elseif turtle.getFuelLevel() > 30 then
        write("Fuel is over 30, no need to refuel")
        sleep(1.6)
        term.clear()
    end
end

function mine()     --the function for mining, to 100 block long strips. with sand/gravel protection
    if turtle.detect() then
        turtle.dig()
        sleep(.5)
    end
    turtle.digUp()
    turtle.digDown()
    turtle.forward()

end



intro()
cFuel()
input()     --nothing yet
                    --script starts here
while true do


if i%6 == 0 then          -- problem is here
        turtle.select(2)
        turtle.placeDown()
        turtle.select(1)
end

for i = 1, 100 do

    mine()
end

turtle.turnRight()  --turns right to start a new strip, leaves 2 rows then mines.

for i = 1, 3 do
    if turtle.detect() then
        turtle.dig()
        sleep(.5)
    end
    turtle.digUp()
    turtle.digDown()
    turtle.forward()
end

turtle.turnRight()

for i = 1, 100 do   --mines for another 100 blocks

    mine()
end

turtle.turnLeft()       -- turns left to mine a new column (zig-zag look)

for i = 1, 3 do
    if turtle.detect() then
        turtle.dig()
        sleep(.5)
    end
    turtle.digUp()
    turtle.digDown()
    turtle.forward()
end

turtle.turnLeft()
end