Parametric Thermos Script

Problem/Feature Description

A product design team is exploring parametric 3D models for a stainless-steel thermos flask. They need a JSCAD script they can use as a starting point for fabrication prototypes. The thermos has a tall, gently tapering cylindrical body that widens slightly in the middle and narrows toward a short neck at the top. The neck is topped by a flat lid that overhangs the neck slightly.

The team wants the script to be parametric — all proportions should be expressed relative to the total height so that the design can be scaled up or down simply by changing one master constant. They also need the body surface to be smooth enough for render previews. The total height should default to 220mm.

Write a JSCAD main() function that generates this thermos shape.

Output Specification

Produce a single file named thermos.js containing the complete JSCAD script.

The script must define a main() function that returns the assembled thermos geometry. Do not produce any other files.