pinhole camera
The basic idea is to allow light to shine through a small opening. The hole acts as the lens of your camera. It doesn’t focus the light like a regular camera does, but since the hole is small it creates an image of your light source (like the Sun). Since light travels in a straight line, light coming from the left of the hole will reach the inside of the box slightly to the right. Light from the right will travel through the hole and to the right, and so on. As a result and image will appear on the inside of the box.