1. Explanation of onion skin. This is a function that allows you to see through the pictures of the cels before and after. Simple and easy to use. On the right is the light table. Not used for onion skin (just left for illustration purposes)
2. Explanation of the light table. The cell ① is drawing now. ② is an illusion. In other words, a copy of the specified cell is placed as the material. You can scale, move, and change the angle. When putting an illusion in ②, it works well if you select multiple cells that you want to make into an illusion and then select the bottom right. There are some tricks, so practice until you get used to it.