Keystone effect

Keystone effect is like when you build a super cool castle with blocks, but the blocks are not properly aligned, and the castle starts to look like it's falling. It happens when you project an image or a video onto a surface from an angle that is not straight, which gives the impression that the image is distorted, like a trapezoid.

Let's say you have a projector and you want to show a movie on a whiteboard. Normally, you would put the projector directly in front of the board, and the movie would look straight and not distorted. However, if you put the projector on the side of the room, the movie won't look like it's supposed to. Instead, the picture will be wider at the bottom than at the top, and the movie characters will look fat and squished.

There are ways to fix the keystone effect. One way is to move the projector closer to the center of the screen so that the angles are less extreme. Another way is to use special software that can adjust the image to make it look straight again.

So, keystone effect is when the picture you want to see is twisted or distorted because of the angle you're looking at it from, but there are ways to fix it!