First things first, thank you for setting the default music volume as low as you did.
I liked the clean and easy to understand UI. I had trouble drawing routes, it felt like I was doing something wrong, but couldn't figure out why. Some feedback on what goes wrong when failing to create a route would be nice, as I didn't think that there would be a max route length until later in the game.
One of the routes I drew didn't get the blue line, but the trade route did count as I saw a ship moving back and forth between the two planets. So not a game breaking bug, just wanted to let you know.
I liked the style too, very pleasing to the eye. The game did feel a bit slow at times, with downtime I just spend waiting, but this is probably me playing the game in a non-optimized way, or perhaps a matter of polishing a bit more in terms of prices for upgrades and such, better allowing the player to get that snowball running. This is also something that I need to look more into in my own game, that's for sure!
All in all a very nice and cohesive game, especially considering that you made it yourself. Well done!