Introduction: Classroom Warfare!

This is my first instructable and I am going to enter it into the Converse Back To School In Style competition. Please tell me what you think of this instructable as I plan to make a larger version of this out of wood and on a rather large scale. This instructable will teach you how to create a slingshot/catapult for ths classroom.
!!WARNING!! This is only a fun instructable, the end result can create alot of force and aiming at someone could seriously hurt them, I advise you not to fire it at people unless you plan on getting in trouble.

Step 1: Items Needed

I have taken a picture of a few of the items required, but there are more than that!

8 Pens all of the same size.
Plenty of Celotape.
1 x Elastic band.
Another pen slightly longer than the others.

Step 2: Building the Base

Start by putting 2 of the pens at a 90 degree angle and using the celotape to make them firm, this will stop them from moving about. A firm and flat base is needed otherwise it won't fire as well as it should.

Step 3: Finishing the Base

Repeat step 2 until you have a square made out of the pens. The finishing product should look something like this, this will optimise the performance and give max distance.

Step 4: Building the Sides

The sides are the most important part of the "Weapon", they must be strong, but using school supplies doesn't make this the easiest thing in the world. Place 1 pen at either end of a side, and celotape it into place.
I have used coloured pens to make this easier to see. The yellow pens are to be used as the sides, and the red pen ( On the base) is the front. Place a remaining blue pen close to the red (base) pen and celotape it in place. I have done them at roughly a 75 degree angle, it doesn't need to be spot on, but something close to this will help. Now place a remaining red pen near the blue (base) pen and celotape it in place, this pen is at roughly a 65 degree angle.
Once this is done, celotape where the pens meet, but make sure there is a "V" shape sticking off the top of the pens.

Step 5: Adding Stability

Once you have made the sides (Repeating step 4 on both sides) you will need to add stablity as the sides are fairly weak. Face the catapult forward (Away from you) and take your remaining pen ( The one that is longer than the others). Place the pen between the red pens so it pushes them out slightly. The force of the sides pushing against the pen should hold it in place, but to make sure it stays like that you are going to celotape it in place. This will make the structure alot stronger.

Step 6: Adding the Launcher

With the catapult facing away from you once again, you should have the 2 blue(side) pens facing towards you. All you are going to do is simply place the elastic band over the blue pens. This will give you your launcher. The longer the pen in the middle (Pushing the sides apart) the more tension on the elastic band, so in theory, the futher it will fire something.

To fire: Place your hand/arm through the slingshot (Under the center pen) and rest on the blue and red pen(Base). Pull the elastic band back with your choice of ammo on it and fire away!