This is my advanced tunneling program:

It digs a 3x3 tunnel up to 64 bricks long, placing a block in the floor (preferably glowstone) every 5 bricks. It can also build bridges and place a trail of blocks. Specifically, I built it for making train tracks. Instead of returning to the start when it hits a mob, it will keep trying to head forward.

It is currently in very earlyt stages and I need a lot of feedback to improve it.

Instructions:
Place the block to be laid down behind the turtle in slot 1
Place the block to be set in the floor (use glowstone) in slot 2
Place the bloock used to build bridges in slot 3

It has three options: the length, whether to lay blocks behind or not (Y/N), whether to light the tunnel (Y/N), and whether to build bridges (Y/N)

Examples:
advtunnel 64 Y Y Y (64 bricks long; yes to all options)
advtunnel 54 Y N Y (54 bricks long; lay a trail of bricks, do not light the tunnel, build bridges)

If you're making a train tunnel with it, I reccomend the following bricks:
64 train tracks in slot 1
at least 13 glowstone in slot 2
64 wood planks or stone in slot 3
advtunnel 64 Y Y Y

The image uses the following options:
advtunnel 64 N Y Y