Great Game
That game was really great. It gets really hard after level 50. I made 5-6 missile towers and an upgrade to missile turret, these towers rockzzzz. The Dcas are very important after level 15, u should build them as soon as possible. The vulcano cannons are really good, it is very cheap( 35 gold) to bring them on level 3, they make there 40 damage, thats good for only 40 gold. Some sniper turret around the exits are really helpfull cause they shoot a lil bit out of the bounds.
The freeze turrets arent very helpful, they r just expensiv, the sonic turrets are good too but u must grade them up to level 4 or 5.
The Plasma towers aare good if u build them to a strait but u must grade them up, thats the most important thing at the game.
I found the game really good, i wish i would have the save funktion in higher levels, u must do something with the bug that the aliens splash trough the turrets. The game is a bit hard but it is really funny..