How would you design a lunchbox that could keep hot food hot or cold food cold sketch a diagram of the box?

To design an effective lunchbox that maintains temperature, I would use a double-walled insulated structure filled with vacuum-sealed air to minimize heat transfer. The outer layer would be durable, waterproof material, while the inner layer would have separate compartments for hot and cold food, each with its own insulation. A built-in heating element for the hot compartment and a gel pack for the cold one could enhance temperature retention. Additionally, incorporating adjustable vents would help regulate humidity and temperature inside the box.

(As I can't create sketches, I recommend visualizing a rectangular box with two distinct compartments—one for hot food with a heating element and another for cold food with a space for gel packs, all enclosed in a durable outer shell.)