为特定语言定义无上下文的语法

I have a language where each string in the language has even amount of 0's as 1's (eg. 0101, 1010, 1100, 0011, 10 are all in the language). I was hoping to define a context-free grammar that describes this language. After defining a context-free grammar I want to formally prove that this context-free grammar describes this language. I have a language where each string in the lang