This scene shows a crossroad with four traffic lights (North, South, East, West). Each light independently follows a 3-color cycle: Red (4s) -> Yellow (4s) -> Green (4s) -> Yellow (4s) -> Red. Currently: North light is red with 4s countdown, South light is green with 4s countdown, East light is green with 3s countdown, West light is yellow with 1s countdown. Simulate 6 seconds and show the final state of all four traffic lights. Only modify what the task requires; keep the background and any other element unchanged. Output one image per second of the countdown (every time a number changes or a light transitions, write one image). The last image shows the final state.