Nice, relaxing game, without getting boring! Pretty original, it looks awesome as well and plays well, I always find it frustrating with these type of games when the steering is buggy, but everything works exactly as expected. Very cool! Also, the upgrading and assignments give enough incentive to try again, and again, and again.
Goed gedaan! :)
An improvement suggestion, it could add to the difficulty if you do not allow your roots to cross each other. I was kinda avoiding that until I noticed that is not needed :)
And agreed with a previous comment, it's already a good and complete game, but it has so many opportunities to extend the gameplay!