固有振動
There are two game modes: Normal and Endless, in which both contain maps with easy, medium, hard, or madness difficulties to choose from. In Normal mode, there is a set number of enemy waves and a set amount of coins to win. In Endless mode, the waves of enemies are endless. This mode also includes a Sandbox option, which starts off the player with 10,000 coins and a speed boost of adding and upgrading towers before sending the endless waves of aliens.