If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
The goal of the game is to destroy the enemy bunker or all of the enemy's unit. To select a unit, press the letter or number above it while on screen, If you wish to select a unit hold over shift key and the corresponding letter/number shown on the unit.
WASD- To scroll view.
Space bar- To view remaining units.