Alien Syndrome is a typical topdown action game, where the mission is to kill the nasty aliens and save your crewmembers, before killing the boss. All before the time runs out and your ship explodes in space.
You play as either a guy or a girl, and you start off with a simple gun. Along the way you will find compartments filled with goodies and map centrals (usually next to each other) to help you get better weapons, and to see where you should go to save your team-members. Just walk up to these consoles and you'll get access immediately. I haven't been able to figure out if the different weapons do different amounts of damage, as most things die after a single shot. But I know that the little robot that you can get is very useful for keeping your back cleared of aliens.
The only thing I find negative about this game is that you have to almost be at the edge of the screen for the screen to move around. It is extremely easy to walk into an alien and die as a result from this. The rest of the game is top-notch for its time.
Made in 1989, it is really good looking for its age and plays really well.
I would suggest that you turn the cycles down in DOSBox, as the game is time based.
Unfortunately, you will need to either have DOS or use DOSBox in order to get it to run