Lets get started!
Step 1: Materials
a pen similar to the one shown
thats all you need!
Step 2: Make the Pen Gun
First, disassemble the pen. It should look like the picture.
Put the balloon on the end of the pen barrel, and make sure the balloon is not very tight against the pen.
Secure the balloon with the rubberband.
Step 3: Fire the Pen Gun
To fire the pen gun, put the ink cartridge into the barrel