"This is just a simple TD game, it has towers and it has creeps, what more do you need"
A reason to play it instead of the other 25,000 tower defense games?
After playing 20 seconds you know what will happen for the rest of the game. They'll come faster until you die. I suggest an option to disable sound, that the posters far away (and smaller) be worth more points, and something to snaz it up.
Actually way too easy. But the hero and flying units go where you tell them to for a whole half second, you spend half the time just telling them over and over where to go.