How do you beat level 3 in plasma burst

You have choice: 1. before you do level go to the "shop" and upgrade gun #2 or 2. do the level but the 1st thing you do is change your gun to gun #3. Then quick start shooting the middle of the glass even when it breaks. Don't stop shooting until you stop hearing a guy going "ahh" or "yai" or whatever the say when they're being shot. Then to deal with the guy who shoots two red lasers at a time. You just have to throw a grenade with the G button on your keyboard right where you're standing. When the guy who shoots the red lasers is dead walk by him and you should pick up his gun. DO NOT GO IN THE ELEVATOR!!