The arsenal is the weapons you have available. To use a weapon click the number on the keyboard. The Laser bolt does require you to aim with the mouse. The Clone Trooper walks across the battle and has a chance to either kill a battle droid or be killed by a battle droid. Red Squadron will nuke the battle field killing all battle droids. Your objective is to fight against the oncoming battle droids and stay alive.
The level cap for the BETA is level five the full game will have five more levels and I am not sure how many more ability's will be in your arsenal in the full game (I will add some I just don't know how many more). It's also a possibility that I will create harder versions for those who like a challenge.