The gameplay of
Spacewar involves two monochrome
spaceships called "the needle" and "the wedge", each controlled by a player, attempting to shoot one another while maneuvering on a two-dimensional plane in the
gravity well of a star, set against the backdrop of a starfield.
[2][4] The ships fire torpedoes which are not affected by the gravitational pull of the star. The ships have a limited number of torpedoes and a limited supply of fuel, which is used when the player fires his thrusters.
[6] Torpedoes are fired one at a time by flipping a toggle switch on the computer or pressing a button on the control pad, and there is a cooldown period between launches. The ships follow
Newtonian physics, remaining in motion even when the player is not accelerating, though the ships can rotate at a constant rate without inertia.
[2]
Each player controls one of the ships and must attempt to shoot down the other ship while avoiding a collision with the star or each other. Flying near the star can provide a
gravity assist to the player at the risk of misjudging the trajectory and falling into the star. If a ship moves past one edge of the screen, it reappears on the other side in a
wraparound effect. A
hyperspace feature, or "panic button", can be used as a last-ditch means to evade enemy torpedoes by moving the player's ship to another location on the screen after disappearing for a few seconds, but the reentry from hyperspace occurs at a random location, and in some versions there is an increasing probability of the ship exploding with each use.
[6]
