I like the idea, it reminds me of the game mini metro. I had the game freeze completely twice, I am not sure what caused this. Both times I spent an extended amount of time with the line in a dead end with nowhere to go, maybe the game got stuck trying to find a viable spot to go to. But when I tried to confirm it it didn't happen. It might also be good to mention that you can cancel by right clicking, in the game description.
I'm interested to see what you will do with this game, I think there is a lot of potential.