This is a two player game similar to Rock, Scissors, Paper; players decide what to do and reveal their choices simultaneously. You win by outguessing your opponent. If you play many games you might detect patterns in your opponents' play that you can use to your advantage.
Each player is in command of a starship meeting an enemy starship in deep space. Each ship starts with 3 missiles and enough energy to power its shields 6 times. The game is played in rounds.
In each round each player can fire one missile, power its shields, do both, or do neither. Powering your shields stops an incoming missile. The power used to power your shields is used up whether the enemy fired or not. If a missile is fired at an unshielded ship then the ship is destroyed and the game is over.
If you destroy the enemy starship and your own is still intact then you win. If both ships are destroyed or both run out of missiles without destroying each other then the game is a draw. If you run out of missiles and your opponent still has at least one left then you lose.
For face-to-face play a referee isn't needed. Players can use pennies and dimes or different colored Risk pieces for missiles and shields, hide them in a fist, and open them simultaneously.