Hi there! I understand you're having trouble closing the 5 Differences Online game on your Windows 10 device using WebKit browser. To help you get this sorted, can I ask:
- Are you trying to close it from within the game interface, or have you tried closing the browser tab/window?
- Does the game freeze or is it just not responding to the close command?
- Have you tried any steps already to close it?

Once I have a bit more info, I can guide you step-by-step to close the game properly. Meanwhile, here are some straightforward methods you can try:

1. Try closing via the game menu: If there is a "Quit Game" or "Exit" option inside the game, use that first.

2. Close the browser tab or window: Just close the tab where the game is running. If it doesn’t close, try closing the entire browser window.

3. Use Alt + F4 shortcut: Click on the game window to make sure it's active, then press Alt + F4 on your keyboard. This shortcut forces the current window to close.

If those steps don’t work, we can try some Windows-level options:

4. Use Task Manager:
- Press Ctrl + Shift + Esc to open Task Manager.
- Under the "Processes" tab, look for your browser or any process named related to 5 Differences Online.
- Select it and hit "End task" to forcibly close the game process.

Let me know if you’ve tried any of these or if the game responds differently. We’ll get this fixed!