Press space to pause at any time. There are special missiles in the game, including one that will reverse the polarity of your mouse, make sure to keep an eye out for them.
MIRC (Magnetic Impact Resistant Cubes) is a Missile Command clone with a unique twist. Click anywhere on screen to create a "magnetic force" that repels your cubes. With proper timing you can levitate your cubes into the air and launch them into the incoming missiles to protect your base.