Kill enemies by pressing the corresponding letter on the keyboard. Hit SPACEBAR to drop a Panic Bomb that will destroy all the enemies on the screen at once. Kill Bonus Letters to complete the words 'LIFE' or 'BOMB' and get, respectively, and extra life or an extra Panic Bomb. Use the 'Pause/Break' key to pause the game. Kill the aliens as last as possible to get a higher score (max 100). Don't let the aliens hit your city. For each block of it that you save you'll be awarded a bonus score at the end of the stage. Also if you destroy all the enemies in a stage you'll get 1,000 extra points! Accuracy is important, don't hit your keyboard randomly as your bonus at the end of the stage will be modified by your accuracy level. During Bonus Stages, enemies can't damage your city as they'll fall into the water. So try to score as many points as you can! You'll earn 10,000 extra points at the end of each Bonus Stage if you kill all of the enemies!