Like other games in its genre, the game's basic premise is simple. The game is played on a set map, in this case one resembling an office desktop. The player must stop a set number of enemies, known in the genre as creeps, from reaching a set point on the playing field. This is accomplished by building and upgrading towers that shoot at, damage or somehow hinder the enemy creeps before they are able to reach their objective.
The player has a set number of lives that diminish every time a creep gets through the defenses he or she has built and reaches its objective point. Upon loss of the last life, the game is over and the player is defeated.
The game can be played in three difficulty levels, aptly named easy, medium, and hard. In addition, there are several "challenges" available in the challenge mode for those seeking more from the game. Challenges range from "The 100," where the player must defeat 100 levels of successively difficult creeps to "3K Fixed," where the player has only a limited amount of gold to build his towers. There is also a fun mode with various sub-modes quite different in gameplay from the other, harder ones.
Aside from English, the game is also available in Spanish, German, French and Italian.