Interesting design! It would be awesome if there was a longer campaign with a far wider variety of shipments whose successful delivery determines which turrets and upgrades you can use for future deliveries. Great, smooth programming!
Thank you for playing our game! We really appreciate the feedback and we hope you enjoyed playing.
The idea of shipments unlocking upgrades is an idea we've had floating around for a while, but sadly we couldn't fit it in before our deadline. If we end up continuing work on it, it's definitely being considered :)