How to do pinhole imaging?

The pinhole imaging manufacturing method is as follows:

Firstly, put a piece of white paper on the desktop as a screen, put a piece of hard paper with a small hole in the middle between the incandescent lamp and the light screen and fix it on the bracket;

Then turn on the light switch, and you can see the image of the filament on the light screen. The opening of the image is opposite to the opening of the filament, which means it is inverted.

Moving the position of the hole up or down can change the size of the image; If the holes are changed into small squares, rectangles and triangles respectively, their imaging will remain unchanged, indicating that the imaging of the holes has nothing to do with the shape of the holes.