This simple "hologram" device (it's not actually a hologram, obviously) could spice up any game, no matter whether it's a sci-fi campaign with hologram devices, or a fantasy setting with a magical beacon projecting an image. There's a lot of fun to be had with this simple tool.
Creating something that can create the hologram illusion is very easy and cheap too, as you'll see below.
Parental guidance: Use of a hobby knife or scissors.
Time: 15 minutes
Cost: Very cheap, especially if you recycle a plastic bottle or something similar.
Materials: Hobby knife or scissors, transparent tape, plastic or printable transparent sheet, ruler, pencil or pen.
Optional materials: Ruler.
Firstly, let me clear up what kind of plastic you need. You can use any fully transparent plastic, as well as similar materials. So you could recycle a plastic bottle to cut down on costs even more (plus recycling, yay!). I do recommend using straight plastic, as it'll make the creation process much easier. If you've got curved plastic, try straightening it first.
The creation process is very simple and straight forward. First you'll want to gather your materials, clear a good space to work in, and start measuring and drawing 4 equal, symmetric trapezoids (or trapeziums depending on where you live) onto your piece of plastic. Basically 4 triangles with their top cut off. You can line them up side by side while drawing, just make sure you alter them based on which side is up.
After you've drawn them, simply cut them out. It can help to use a hobby knife and a ruler to keep the lines straight, but it's not necessary.
Note that the bigger the difference between the width of the shortest and widest side, the more at an angle your final result will be. Which can make viewing the hologram effect trickier. For my phone one I used 6.5 cm for the widest side, and 1cm for the narrowest side, but probably would've had a better result with a short side of about 2-2.5cm. I used roughly this ratio for the bigger one found below.
Once you've cut them, stick them together side by side with transparent tape. You'll end up with a square based pyramid with a flat top, like in the image below.
Now all there's left to do is load up a video or image designed for these holograms on your phone (YouTube has a lot), put the plastic creation on top (narrow side down), and enjoy it. For a better effect, turn off or dim the lights in the room.
If you want to make your own hologram images, simply place copies of the image in opposite positions on a cross. Make sure there's enough space between them so the plastic hologram device can sit between them when the image is shown on a screen, and you're pretty much done. If you need a template for the distance, taking an existing image or taking a screenshot of a YouTube clip should do the trick.
You can scale up the tool as big as you want. In the somewhat fuzzy picture below I used 4 A4, printable, transparent sheets, as well as a bigger screen for the hologram effect.