From the map, the player can move the Enterprise to different levels, including Klingon Warship levels, Space Amoeba levels and Asteroid Field levels. The player uses the ship icon at the bottom of the screen to track his progress through levels. The player has two weapons at his disposal while in ship mode: phasers and photon torpedoes. In the power menu the player may choose to divert power to or from speed, shields, or phasers. The Enterprise must defeat many Klingon ships and hit warps and collect energy to advance, while avoiding asteroids and enemy fire, as well as the gravitational pull of planets.
Source: Wikipedia, "Star Trek: 25th Anniversary (Game Boy video game)", available under the CC-BY-SA License.