Mortal Kombat is a fighting game in which players battle opponents in one-on-one matches. The fighter that drains the opponent's health bar first wins the round, and the first to win two rounds wins the match. Each round is timed; if both fighters still have health remaining when time runs out, the one with more health wins the round. Two players can start a game together, or a second player can join in during a single player's game to fight against them. If a game was in progress at the time, the winner continues it alone; if not, the winner begins a new game.
Mortal Kombat uses an eight-directional joystick and five buttons, including two punch and two kick buttons, each further differentiated between high and low. Attacks can vary depending on the player's distance from the opponent. All player characters have a shared set of attacks performed by holding the joystick in various directions, such as a leg sweep and an uppercut; the latter attack knocks the enemy high into the air and causes a large amount of damage. Most special moves were performed by tapping the joystick, sometimes ending with a button press. Unlike previous one-on-one fighting games, few moves require circular joystick movement. The game's blocking system also distinguished itself from other fighting games, as characters take a small amount of damage from regular moves while blocking. However, the dedicated block button allows users to defend against attacks without retreating and blocking characters lose very little ground when struck, thus making counterattacks much easier after a successful block.