I was just thinking yesterday after some observations :

Why must the corners of drains be 90 degrees and sharp?Why not 90 degrees but yet rounded so that water can flow easily.hmm...still thinking about it.Any answers as to why is it sharp?

How can pieces of material be fitted together to make a roof/covering from the rain?(it was raining when i had my thoughts and observations).I know its easy answering stuff..but i had this revelation of 'wow-ness'.haha..if you know what i mean.yep..anyway,just some of my thoughts the other day..haha...