Flat Kit is a complete solution to achieve the stylish cel-shaded look: shaders, models, image effects, presets, examples.
The custom shading model is versatile enough to work great for classic cel/toon shading and for unique styles of experimental
openGL实现（ADS）环境光，漫反射，镜面高光，实现双面（前面front、背面back）着色 实现平面着色（flat shading），使用Subroutines选择着色器功能，Discarding fragments to create a perforated look 丢弃碎片，已实现穿孔效果
题目来源：The Flat Dictionary
一.题目
You are given a dictionary where the keys are strings and the values are strings or dictionaries. The goal is flatten the dictionary, but save the structures in the keys. The result should be the a dictionary without the
