No you are not doing anything wrong. The game is supposed to ramp up in difficulty as soon as you get Guards, but maybe there's a bug I'm not aware of where the rate at which attacks appear is too fast (might be the case), or it could be just RNG having a bad day. Regardless I know the game is poorly balanced and a bit rushed in design, it was made in 72 hours after all, but I just haven't had the time or energy to work on it more, so for now this is the state it is in, I'm sorry :C still hope you enjoyed some of it at least! Thanks for the comment
Well, I know that I am impressed! You say this is rushed and all, but it's a *beautiful* game that looks really neat and detailed, with nice systems in place :)
I really enjoyed taking care of the tree particularly. It's also after that that I realized you could click with your soldiers to fight, and by doing so it gave me some leeway to win more battles and protect my tree for longer! I realized this after I actually managed to quickly read what the cannon did LOL.
After that, I managed to get some other upgrades and I managed to get everything under control again. I was sad to read there's no 'good' ending, but I enjoyed the game either way and it does properly show off going too far and greed!
Overall, I can't even draw a tree or properly do any technical stuff so there is no critique at all here! I loved this game ^^