You have to do, and I hesitate to call it this, a tiny bit of 'arts and crafts'.
Simply, you have to 'peel and stick' one thing...that's it!
There is a modification that you can make to the pen, but it isn't required.
I made the pen mod, but no one really noticed one way or the other...
Plus, learning this is about as easy as it gets. The handling technique is very natural.
For such an easy trick to learn/perform, this thing plays huge.
When you erase the door at the end...INCREDIBLE!