Any projectile motion, or we can use Intel Curie technology of simulation. We can see the difference but it's safe. Please don't target the eyes of life subjects.
Step 1: Firstly, We Need a (soldering) Sucker.
From certain lab, we can get this kind of unused sucker, or used one to be part of this experimt.
Step 2: Pen or Else
Afterwards, we just need a pen, or pencil, magnetic dart (for safety reason) etc.
Step 3: Video/Demo
At last, we just play 'the magic green tech' toy gun. Simply by using our own hand, we can keep repeating it. It's safer than the electromagnetic rail gun, the new weapon of US Navy etc.