Click once to select a letter. Double-click to check the validity of your word. If it is valid then all selected letters will be destroyed.
Press space to fire bullets. You have a limited number of bullets so use them very careful. For instance, fire bullets only to destroy letters which are too close to your tower. For letters destroyed by bullets you don't get any points.
You get points only for a valid word as a total sum of letter values multiplied by length of word. For a completed level you will get a bonus of 500 points. To complete a level you must use a certain number of letters!