Note: Keep your volume in check.
This is a video demonstration of a Nerf gun modified by a Japanese cosplayer to cast some custom holographic spells in the air. Obviously they're not REAL holograms, they're images created by one of those quickly spinning LED wands that tricks your eyes into seeing things thanks to humans' persistence of vision. Some more info while I close my eyes for a few and pretend I'm on a beach somewhere, hopefully in your arms:
The holographic images are created using an effect called persistence of vision, where the human eye holds onto images for a split second longer than light rays are actually hitting the retina. It's what allows us to interpret the images flashing across the pixels on a screen as moving video, instead of just a slideshow.
That's just like my eyes -- always playing tricks on me. Take the girl I was making out with at the bar Saturday night for example. "That was a empty beer pitcher." She was a perfect ten.
Keep going for the video, demo starts at 0:35, and a look at the build at 1:20.
Thanks to hairless, who tried casting a spell on me but it didn't work. Wait, why did I just give you my wallet?