We also made some changes to improve how bonded atoms behave physically. In our initial prototype, each atom in a molecule was fixed to a position relative to the parent, that was calculated according to a database of molecule structures. While this resulted in correct molecule configurations, the resulting experience did not convey why a molecule was structured the way it was, which was that the electron pairs were repelling each other. We therefore experimented with a more physically based approach, where atoms were instead constrained to each other using spring joints, and would repel each other using an approximated force, eventually converging to a tetrahedral shape.