You have to blast the invading aliens as they form in wave attacks and clear them in the alloted time before they turn into superbreeds and become even faster and more dangerous. Successive waves attack even faster in more ferocious and menacing formations.
There are some special features to help you. If you have enough energy units. Smart Bombs will blast all aliens from the screen. If you have enough energy units, Inviso-flight can give you temporary invisibility and hence indestructibility. If you blast the alien energy balloon 12 times and catch the alien energy pack, then your firepower multiplies threefold.
Hit everything that moves. A bonus ship will be awarded at 20,000 points and additionally there are time bonuses.
CTRL - Left, A - Right, * - Up, ? - Down
RETURN - Fire, SPACE - Smart Bomb, SHIFT - Inviso-flight
DELETE/COPY - Pause On/Off, - Quit Game
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