housestyrell:

One of the things that got me excited about it in the early stages was the question of what it should look like. We knew it was going to be stylised, but not exactly how. The producers came along with the suggestion of creating something in the vein of Lotte Reiniger, an Austrian-born animator working in the 1930s and 50s doing silhouette style animations. What we got out of that was a certain simplicity and naivety. We knew it had to be told very graphically with bold silhouettes.