Have you ever wondered how toilets know what amount of water to use when you flush? It is an engineering problem, which is probably why I started thinking about it. Or I might just be weird like that. However the solution is what makes this interesting.
Toilets does not know and in fact they do not care how much water is required per specific case — they simply use a sufficient amount for all cases. That might be too excessive sometimes and just barely enough other times. But it works most often and it is non-complex.
The simplicity and pragmatism is what makes this a beautiful solution.
What kind of toilet are you working on?