Missile command launch missiles to protect your missile turrets to protect them by right clicking at the position you wish to launch them.
The levels are completely customizable from what units can spawn, how many turrets you have, how many depots you have, the area in you must defend, your missiles speed/explosion size, enemy attack speed and movement speed. You can also save these settings for later play. Included 7 premade settings just to show a sample of the kind of scenarios you can play.
Depending on the settings you chose the difficulty can be from Piece of Cake to Impossible.