I'm glad to hear you enjoyed the replayability as that is exactly the style of game we were going for! We thought about allowing the player to not combine tiles, but we liked the idea of each decision having a cost associated with it when you are forced to upgrade. We did a lot f play testing with a paper prototype and this is what we came to. We have also had some talks about possibly further developing the game for a mobile and steam release, we will have to see what our futures hold!