I think this is an really nice game with an lot of potential.
First of all the praphics were just right for this game.
The build up of difficulty was pretty good too, with more different kinds of enemies later on. The upgrades were all usefull, except of the mage one.
But still room for improvement:
-The mage was useless, Easy to fix:
Shortkey on keyboard, this game is pretty much played with only 1 hand,
adding keyboard brings some new elements in game, also can add multiple spells by pressing 1,2,3,4,5 ect.
- The adchievement system, think it's a lil buggy. And i personally don't liek to get adchievements for everything. But that's just my opinion.
-Upgrade menu, maybe even more upgrades. Like adding a wall around, water around the castle. All kinds of upgrades, as long they are usefull and balanced.
Overall really great game, and enjoyed playing it.
Would really want to see Castle Guardian 2.
Keep it up