function OnGUI () {
一些基础的知识，也是比较常用的！
//一个最简单的按钮
if (GUILayout.Button("button"))
print("u pressed button");

//只认可左键点击
if (GUILayout.Button("button00") && Event.current.button == 0)
print("u pressed button00 with left button");

//点击或输入a
if (GUILayout.Button("button01") || (Event.current.type == EventType.keyDown && Event.current.character == "a") )
print("u pressed button01 Or input a");

//Ctrl + 左键点击
if (GUILayout.Button("button02") && Input.GetKey (KeyCode.LeftControl) && Event.current.button == 0)
print("u pressed button02 with left button");

}