Nice tower defense game! I managed to survive for 25 days. I think the main area for improvement is the UI. For instance, your tutorial presents too much information at once, even though the game itself is fairly simple. The same goes for the upgrades or when monsters get hit — players don’t need to see specific numbers everywhere. (I encountered a bug where defense items didn’t cost anything if I had enough money to buy them.) Also, I was confused when I couldn’t place items that were too expensive at first. If I don’t have enough money to buy something, you should prevent me from being able to place it. Overall, nice game that even has an online leaderboard!