If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
You are on a mission and your main objective is to kill all rebel species and destroy their base. Use mouse to shoot, and space bar to throw grenades for base destruction. You will have to destroy all rebel bases to clear the level, check the map for base location.
Use Arrow keys or W A S D to move.
1,2,3,4,5 and 6 to shift your weapons.
Mouse to shoot.
Space bar to throw grenade.