Earth is under attack by a hostile alien invasion force of unknown
size and origin! The object of Alien Invasion is to destroy as
many waves of attacking alien invaders as possible. To help you
in your task, your ship has been equiped with an array of weapons
and counter-measures (described below). Increase the effectiveness
of your ship's weapons, and your ammunition supplies by collecting
the powerups which appear after each destroyed alien attack wave.
This is your ship's main weapon, and is the only weapon
for which you have infinite ammunition. This weapon be upgraded
to fire more shots at once.
This weapon launches a missile which will attempt to home
in on the nearest alien. Can be upgraded to improve the missile's
homing ability. Ammunition for this weapon must be collected.
This weapon fires a singe laser beam, which will cut through
anything it comes into contact with. If well amied, this weapon
can destroy several aliens with a singe shot. It can be upgraded
to increase the size of the beam (potentially increasing the
number of kills with each shot). Ammunition must be collected
for this weapon.
The most powerful weapon available to you, this weapon is
designed to destroy several aliens with a single deployment.
Press the 'd' key once to lauch the weapon, and while the
bomb is in flight, press the 'd' key once again to detonate
it. Once detonated, the bomb will create an expanding shockwave
that will destroy all aliens it engulfs. This weapon can be
upgraded to increase the size of the detonation shockwave
(making it easier to destroy more aliens with each detonation).
Ammunition must be collected for this weapon.
Your shields will reamin activated as long
as you hold down the 'up' (arrow) key. While the shields
are active, you will not be harmed by alien weapons. However,
you will not be able to fire your own weapons while your
shields are activated. Additionally, you have a limited
amount of shield energy (as indicated by a bar at the bottom
of the screen), and once your shield energy is used up,
you will not be able to activate your shields until you
collect more shield energy power-ups.
By pressing the 'down' (arrow) key, you can teleport your
ship instantly to the other side of the screen. Use this feature
to quickly escape bombardments by alien weaponry, or to collect
power-ups on the other side of the screen. The teleportation
device also has the beneficial side effect of confusing alien
missiles which are already in flight, making them unable to
home in on you.
After you destroy each wave of aliens, a power-up will become
available. They will appear at the location of the last destroyed
alien, and fall down for you to collect. By collecting these power-ups,
you can upgrade your weapons (making them more powerful as described
above), or increase your ammunition supplies. Try not to miss