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PolskiInterplanetary Gravity-Assist Explorer (2D)
Launch a probe from a low orbit and let it fly under the true summed Newtonian gravity of a sun and three moving planets — swing close enough to one and its real slingshot effect will bend and boost your trajectory, exactly as it does for real interplanetary missions.
The 3D original is a decorative rotating-cylinder dashboard whose sliders don't drive any real physics; this 2D companion replaces it with a genuine N-body gravity simulation. A sun sits fixed at the centre and three planets orbit it on real Keplerian circular orbits (their angular speed comes straight out of Newton's law of gravitation). The probe's acceleration at every step is the true vector sum of the sun's pull and each planet's pull, integrated with a symplectic velocity-Verlet scheme so long flights stay numerically stable. Fly close enough to a planet's sphere of influence and you get a real gravity-assist flyby: the telemetry panel measures the probe's speed on entry and exit and reports the actual delta-v the encounter added or removed, the same slingshot effect that has sent real probes from Venus to Jupiter and beyond.
2D N-body gravity-assist sandbox: a fixed sun plus three Keplerian-orbiting planets pull on a probe via the true summed inverse-square law, integrated with velocity Verlet, with live flyby delta-v, mission time and fuel-limited correction burns.
2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install
The 3D original is a decorative template with sliders that don't drive real physics. This 2D companion was built as a genuine substitution: a real N-body Newtonian gravity simulation instead of the rotating-cylinder decoration.
The simulation records the probe's speed the instant it crosses into a planet's sphere of influence and again the instant it leaves; the difference is the real delta-v that flyby added or removed from the trajectory.
A symplectic velocity-Verlet integrator with automatic sub-stepping, plus gravitational softening near each body, so close flybys don't blow up into infinite accelerations.