beware of invisible walls

My Creative Design teacher is in her 70's. She still wears mini skirts (with tights) and Bebe clothes. The class room we meet in is enclosed by solid glass walls. I don't know how she did it, but on her way into class today, she ran straight into the glass wall so hard, she bounced into the wall behind her which bounced her to the floor... She hit the glass so hard, bits of her eyebrow were ripped off and left on the glass where she hit. She still taught the lecture. I can't get the image out of my mind.

Invisible walls are not for the aged or hurried.