It's just a simple Three.js live renderer with three shapes already defined: Box, Cylinder, and Sphere, plus an export to .STL feature.

Group welds shapes into one solid, which can then cut, or be cut into:

Group([
  Cylinder({ radius:5, height:20 }),
  Box({ size:{ x:3, y:3, z:30 }, cut:true }),  // notch in the tool
], { cut:true });                              // the tool cuts the model

Groups nest and take their own position and rotation.

The loaded design is SimpleDrone.