Xenotactic

No doubt that one of the best flash games ever is Xenotactic.
This is a simple strategy game where you have to protect our world from aliens which are attacking over.
Aliens moving from one gate to another one, while they are moving you have a chance to kill them and you have 6 types of weapons to do it.
Where is letter F it is DCA to kill and damage Flying Aliens in the begining of their way.

While some of aliens are moving by the ground, some fly over the Vulcan Turrets and borders.
Flying Aliens is the biggest problem since second level.
To get the level through you have to build path like intestine, to hold moving objects as long as possible to kill them for sure.
In each level you can miss only 25 aliens, if more, you'll lose.

In 3rd level you have to be even more careful with flying objects, coz it will not enough of space to build a lot of Vulcan Turrets, so my advice is to put good upgraded Turrets in the middle and try to make path beside them.
As you see there is letter C in the right bottom corner. If you have problems with Moving Aliens, you can always close this way by putting some Weapon there, and all moving objects will go all the way back.
I don't want to mar your pleasure playing this game, so I will keep in secret how to pass 4, 5 and 6 level.
You have to do it yourself :)

You can always play Xenotactic on Flash Ghetto website.