This is a gem of a game. I loved the game concept and the story it tells (and you can feel) about the horrors of trench warfare.
I did reload a number of times after 'figuring it out'. My first attempt was just plotting lines all over as I was clicking and not realizing this was their walking path. On other attempts the first click is placed right away when clicking to start the game....so a few tries started bad due to this.
Very good submission and a pleasant surprise to play.
Edit - also the name for your game is perfect