Alien Sky is an entertaining shooting game. The storyline is very simple: there is an alien invasion threatening Planet Earth, and your spaceship is the only defense line that can prevent the aliens from taking the planet over.
The alien ships attack in huge numbers, so you need to be quick on the trigger. Unfortunately, the game reacts slowly to the mouse clicks, so a player can't shoot fast enough to bring down enemy ships. Also, the ship only moves horizontally, which limits the shooting possibilities.
Besides the spaceships, there are also crab-like creatures that give extra points when you shoot them. During the battle, several bubbles appear. You need to catch them to gain additional ammunition or lives.
Another disadvantage of this game is that the graphics are very simple. This may not be so important in this type of game, but given the developments in graphic tools, one may expect high-quality graphics, especially in a non-free application.
The demo version allows you to play the game for an hour. If you find the game interesting and want to play it longer, then you need to purchase the full version.