If you do find yourself needing to cross another string (be it river, mountain or track) you'll have to pay a one point penalty. As a result you end up creating twisty, serpentine routes to avoid this, and placing higher point-value stations in riverbends or mountaintops to make them tough for others to reach.
Play lasts only four or five turns, making this a quick, 20 minute pastime. The rules are simple enough to explain to an eight year old, but this is by no means kids-only fare; you might introduce it as a warm-up for a "serious games" night, only to find your friends wanting to play it again and again.
By turning steel rails into flexible bits of yarn, String Railway transforms the genre into something more physical and strategically open ended. Breaking from the grid system is far too rare in tabletop games; there's a lot to be discovered by going off the rails.