Tower Defense, one of the big overused game themes.
On one hand, the idea of clearing stages by counter-rushing enemies is rather interesting and quite fun. But there are four big flaws with the game.
One is that as they are passive games, Tower Defense games rely on massive upgrading trees and a high difficulty level to grip the attention span of players. Each level is meant to be a complicated puzzle. And well, although the game does get interesting, it never become really intense.
The other, also linked to the statement above, is that the game is lacking, upgrade-wise, and even seem bugged (cannons, for example, can be upgraded endlessly). The game also lack the ability to undo/sell upgrades when on the field, which is rather frustrating.
The other two are less forgivable. One is that the game is very prone to lagging and very prone to bugging up, objects not showing up. I understand that an unit limit is necessary to keep lag down but if the game cannot spawn more units, the game still eat up your in-game currency, which is blatant fake difficulty.
However, the supreme flaw is that the game is not balanced. At all. All you need to beat the game are wizards and knights. Building any other kind of unit is not only innefficient but suicidal once the enemy make wizards of their own. Simply put? Even unupgraded, wizards are insanely overpowered ; they have an insane amount of life, destroy every unit quickly, they're ranged, and they only cost twice the amount of money of the others (which is a pittance considering a single wizard group can solo an entire army of other units). Mix them with knights to distract enemy wizards and you have the lone viable strategy for the entire game.
Yay.
The concept of a game where you counter-rush your enemy is quite interesting but well, I think that the flaws above should be fixed at the very least.
If you plan on making a sequel, a few suggestions...
-have enemies have towers of their own in later stages.
-make it possible to have your fort(s) target more than just a single fort.
-have forts that are reduced to 0 stop spawning troops.
-have tower upgrades be more strategic ; have upgrades have do more than just increase damage and range as to make towers other than the Ice Tower viable.