Enemy submarines have invaded your perimeter. Fight back and sink them all!
Turn your sonar online to locate your enemies, but beware that it gives your position away! Turn your sonar offline to disappear from their radar, and them from yours...
Arrow/WASD (ZQSD on French keyboard): Move your submarine. Space: Fire a torpedo.
F or O: Toggle your sonar online or offline.
P: Pause or resume the game.