How were the Smurfs cartoons made in the 1980s?

In the past, most paintings on the desktop would emit white light. Painters usually take out a few pieces of paper and throw them on it. Light can penetrate these paper layers at once and then turn them over when painting. It's hard. Later, the advanced point is illustration, usually the background version, with many pictures of the same person with different actions. I threw myself on the table and pressed the glass. A vertical camera hanging above the table took pictures. Then put another action on it and repeat the above operation, so that there are many backgrounds and character materials that can be reused. Anyway, I know that Conan's early animation was shot in this way, and now this method is definitely used as a puppet or sticky puppet animation. Then it is basically PC software operation. . . . . .