Slinky

Longitudinal Waves - Covered.

Transverse Waves - Covered.

Pupil engagement - pretty reliably covered.

Not as good as the classic metal slinky but does a job.

Once tangled, never the same again.

This model is a poor performer on stairs and doesn't make that lovely noise that the metal model does.

Newer doesn't mean better.

The joy of slinky.