If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
In this game you have to fight off all the incoming enemies with your sword. The enemies will come in from the ground, and from the air. Most enemies seem to carry a gun as well. Pickup the power ups to gain more strength, needed to survive. Skirmish is a beautiful designed game that seems to simulate day and night effects as well.
WASD keys to move.
Mouse to attack.
1-3 to switch weapons.