Two modes for a single-stage epicyclic set. Common lets you pick two gears, solves the third, validates spacing/collisions/GCD/hunting, and can suggest the nearest valid trio. Search flips the task: for a target ratio, it scans tooth ranges under the same rules to find matching sets. Either way you can animate the scheme, tweak pressure angle, clearance, backlash, display fidelity, and export SVG/DXF. Have fun.
Use it as a planetary gear calculator, planetary gear ratio calculator, or planetary gearbox calculator to lock geometry (Zr = Zs + 2·Zp) and export SVG/DXF.
It also works as an epicyclic gear calculator/simulator: Common mode solves the third member, Search sweeps ranges to hit a target ratio.