I started this but got stuck on that

I started what I thought was going to be an easy and fun project which involves this:

And these:

Instead I can't find something I want to add to the project. There are a zillion places it could potentially be and I can't remember where.

So instead of a finished project I have this:

And a couple others like it. I guess I'll just call this spring cleaning and take the opportunity to make some space!

(Do you spy my ping pong ball gun? That thing is SO much fun. Heh heh.)