lumberjack

local args = {...}
if args[1] == nil then
    print(args[0].." <radius>")
    exit()
end

function FellTree()
    while turtle.detect() do
        turtle.dig()
        if turtle.detectUp() then
            turtle.digUp()
        end
        turtle.up()
    end

    while not turtle.detect() do
        turtle.down()
    end
end

function DetectInSpiral(radius)

    for i = 1, radius do
        for j = 1, i do
            if turtle.detect() then
                FellTree()
            else
                turtle.forward()
            end
        end
    end
    turtle.turnRight()
end

DetectInSpiral(args[1])