Solver for planetary interactions. Plotted are different frames of a test simulation where circles are drawn around each center of mass node in the parent integrator (Hermite0), where the linestyle indicates the type of subnode: black solid indicates a single particle in the parent code, blue dotted a two-body Kepler solver, green dash-dotted a general N-body code (Huayno) and red dashed a symplectic planetary integrator (Mercury). The green dots are stellar systems, the plusses are planets.