This game is a hybrid between a tower defense game and a bullet hell game. Be careful, however, since you can't sell your bought towers.

There are four different types of towers you can purchase within the game:

Basic Turret: This turret is your good old machine gun tower. Does good damage to one enemy. Costs 5 gold.

Cannon Turret: This turret does an aoe effect around the enemy it's bullet hits. Does less damage than the Basic Turret, but it can damage multiple enemies at once.

Thumper Turret: This turret acts much like the Cannon Turret, however it's range and damage is larger, and the attack is centered around itself instead of the nearest enemy.

Time Dilation Turret: This turret slows down all enemies and hostile bullets by a factor of 0.2. It's effects can not be stacked.

Update 19/06/2012:
Made the 'Uhh.... Wait. How did you do that?' badge worth 100 points instead of 50.
Basic Turret's fire rate has been slightly lowered. It's damage has also been cut in half
Cannon Turret's fire rate has been increased. It's damage is slightly lower
Thumper Turret's fire rate has been increased.
Enemies now fire quicker from when they spawn, but still have the same fire rate.
Enemies do not get as fast as quickly now.
Optimizations to help the game keep running smooth.