Santa Claus Gift Factory - JS (Asynchronous) project

The project is to build a gift factory. The user can select gifts with various size (small, normal, big) and each size has an associate weight (1 kg, 2 kg, 5 kg).
After selecting a gift, the dwarf prepare it. He needs some times to make it. When, it's done he put it in the sled.
The sled cannot contain more than 12 kg. In fact, the dwarf will refuse to prepare the next gift if the sled is completely full. At the end, you can deliver the sled with the santa claus. Be careful ! When the reindeer are hungry, the delivery will fail.