I will present a study of gravitational collapse in confined spaces employing the simplest two-body setting: a system composed of two thin shells in spherical symmetry. This double-shell model exhibits critical behavior and chaotic dynamics, both of which are reminiscent of the turbulent instability of anti-de Sitter spacetime recently observed in the evolution of massless scalar fields. The problem amounts to solving just two decoupled ODEs but it captures highly non-trivial dynamics: depending on initial data, one observes prompt collapse, p
