Understanding the logic behind the Tunnels

Download the file tunnels.lvl and open it in LaserTank.

When there are more than two tunnels of the same ID, then when you enter
one of them, you will go out at the first free tunnel of this color.
By 'free' I mean the tunnel without anything on it (antitank, block). By
'first' I mean the first tunnel counting from top left corner (A1): A1,
B1, C1, .... - from left to right, then from top to bottom.

For example: There are four red tunnels: at B3, O3, A5 and G9.
When all of them are unoccupied, so you can enter them, then:
- when you enter B3, you'll go out at O3
- when you enter O3, A5 or G9, you will go out at B3.

When you push a block into, let's say, A5, it will move to B3.
The tunnel at B3 is not free now.
Now, O3 moves to A5, and A5 and G9 - to O3.

Experiment with the level and it will became clearer.

This text was written by Arek Wysocki