Alien Invasion is an arcade shooter similar in most aspects to Space
Invaders and its myriad of variants. The player controls a lone ship at the
bottom of the screen which can only be moved along a horizontal axis. The goal
is to destroy as many alien waves as possible. The aliens appear at the top of
the screen and move from one side of the screen to the other in order to avoid
being hit. The player’s ship has several weapons installed: a blaster with
infinite ammunition, a missile launcher, a laser and cluster bombs.
Pulverizing enemies may drop ammunition and upgrades to the existing weapons,
such as multiple shots for the blaster, an improved homing device for missiles
and a larger shockwave for the cluster bombs.

Since the aliens shoot back, the player has access to some defensive moves as
well. When activated, the ship’s shields can absorb any enemy projectile, with
the downside that the weapons can’t be used while they’re on. The shields can
be used for a limited time and must be recharged by picking up any power-up
dropped by destroyed enemies. In a pinch, the ship can be instantly teleported
to the other side of the screen; this move can be performed an infinite number
of times.

Alien Invasion