Refract

that broken straw was never broken.

drag a beam across water — watch it kink, and the straw snap

The straw was never bent: light changes speed crossing from air into water, and that puts the kink in its path. Push it steep enough from underwater and past a critical angle none escapes: the surface acts like a mirror.

Concepts: light, refraction.

An interactive you play with one thumb, on Wundr.