Farther means slower. Drag your own world out from the Sun and watch its year grow longer and its walk round the Sun grow slower — the rule Johannes Kepler found in 1619, which every planet follows.
Four rooms: Orbit (your world and the real eight, with challenges), Years (your age on every planet), Weigh me (a scale and a jump on every world and the Moon) and Spin (why a day on Mercury is longer than its year). English, 日本語, 中文. Part of Zoey's Lab.