Technology contains fun

Technology has become an essential part of our everyday life. And it certainly can be fun.

Who doesn’t have a cellphone nowadays? Each and everyone of us spend so much of our time checking those perfectly-coloured screens for the latest updates on our work, or just fresh news from our social media feeds.
Technology contains fun. Look at this below. Have any idea what it is? These are two privacy screens, which show or not show the object when looked at directly or at a 28-degree angle.

An invention that has proven so useful for many of us. What do you think are other very useful inventions?