Therefore it has to be well maintained.

It is absolutely not recommended to open it and grease the little rollers with cooking-oil, or to rub them with fingertips after we were fixing a car, so our fingers are still covered with layers of machine-grease.

It would affect their proper functioning very much - namely, the friction between them and the mouse-ball, which, on it's part, is so vital a part, that if by chance or mistake you throw it out of the window, or into a water-well, or a toilet, you can freely send the rest of the mouse same way.

The clicking buttons, on the other hand, are SO sensitive, that if we hit them just a few times with a huge hammer or a fat steel rod, they will be seriously damaged. Be free to try this on your mouse and you'll see!

But try testing the sensitivity of the whole mouse to phisical hits! Take your mouse, throw it a couple times against the wall the strongest you can, and watch the result. Already after the first blow, if you've thrown it really strong, there is very little material for further throwing. Most of it is already under the couch, on the TV-set, and in the vase.

Furthermore, mouse is extremely sensitive to being rolled-over by a steam-roller.

You must try this: if you go over a mouse A with a steam-roller B (espec. if you do it more than once), you shall see that it's become rather flat; in fact, first it crushed into microscopic pieces (almost a dust), which then "glued" into a thin and compact, but hardly reckognizable crust on the ground. Just one glance is enough to tell that there is no cursor any more, that THIS mouse will succed in moving.