Good job! I ran into an issue where the mouse pointer left the game view/port. I had that same issue with mine. For the solution, look up "cursor locking" for webgl in Unity's manual. They have some code you can attach to an object in the scene that will make it so that the cursor stays in the game port unless the player presses Esc. Anyway, nice take on the theme, nice mechanics (I love tower defense games that allow the player to participate directly in the fight), nice use of sound and music.