engineering design
Human nature can be roughly divided into two categories: elemental phase and animal phase. Element phase is a lot of elements between heaven and earth, such as fire, water, wind and thunder. And this whole animal stage is the beginning of Terran legend. The supreme strong wanted to strengthen the power of the Terran, so he took the spirit of the beasts and blended it into the blood of the Terran, thus giving birth to the so-called phase of the beasts. No matter the element phase or the animal phase, there are levels, and it is easy to understand from one to nine.
There are nine products, seven to nine products are high, and those who can achieve the seven products can be called fine products.
In high-quality products, there are two levels of subdivision, which are not available in the first to sixth products, so we can also see the gap between them.