课堂实验交通灯源码，交叉路口上状态切换次序为（复位）红红－红绿－红黄－绿红－黄红－红绿。南北和东西分别对称。-Classroom experiment traffic light source, crossing state switch on the order (restoration) red red red, green, yellow and red--green red-yellow, red and green- North and south and things were sy