That reminds me of an instance where a not-too-bright fellow was stressed out about some exam. He strapped a LED blinker to a clock and a box with rocks, put it

That reminds me of an instance where a not-too-bright fellow was stressed out about some exam. He strapped a LED blinker to a clock and a box with rocks, put it at the basement floor corridor and informed teachers about a bomb he "found just laying there". Everyone was evacuated. A bomb squad had to come from 90km away to disarm it. The kid was expelled after he admitted doing it after questioning. Moral of the story: don't teach kids about LED blinkers.