Light Cells Activation
Build a 3×3 grid of light cells (omitting the center cell) where you can click on the cells to activate them, turning them green.
When all the cells have been activated, they will be deactivated one by one in the reverse order they were activated with a 300ms interval in between.
This problem asks you to implement a 3×3 light grid with the center cell omitted. Clicking a cell activates it and turns it green, and once all cells have been activated, they must be deactivated in reverse activation order with a 300ms delay between each step. The key idea is to track activation order in a stack-like structure and replay it backward using timed updates, which tests event handling, state management, and timer-driven UI behavior.
