Controlls:
A - shoot gun
S - throw grenade
P/ENTER - pause game

You can get a new weapon, for a short amount of time by getting a POWERUP ORB. Each orb has a different color, and each gives you a different gun. Once you have a new gun, you only have a certain amount of time, the most powerful guns having the shortest amount of time. To kill a boss, you shoot him until he dies. You can also get more points/life by getting a LIFE ORB. Life orbs have a little white dot inside them, and come in 3 different colors.