[\begin{align} p _{n+1} &= p _n+K\sin(x_n) \mod 2\pi\newline x _{n+1} &= x _n +p _{n+1} \mod 2\pi \end{align}]
based on Complexity Explorable:
"
Kick it like Chirikov

Explore the chaotic sea of a famous twodimensional map
"