Four waves. Not for sale yet.
Nodes on a string
Both ends stay fixed. A harmonic number n = 2 × length × frequency ÷ wave speed. Nodes, counting both ends, are n + 1.
That's the four.
A speed slider is coming. Not for sale yet.
OpenStax, Physics, chapter 13. Waves and their properties. CC BY 4.0. The drawing is original.