Fullscreen Mode: Added a fullscreen option to the resolution settings.

Input Adjustments: * Fixed the [Esc] key to the "Back" function.

Removed the "Return to Title" function from the [Enter] key.

Keyboard Shortcuts: Added the following shortcuts:
[Alt] + [F4]: Close the game.
[Alt] + [Enter]: Toggle between Windowed and Fullscreen mode.
[Ctrl] + [Z]: Undo (Same as the "Back" button on the puzzle screen).
[Ctrl] + [Y]: Redo (Same as the "Forward" button on the puzzle screen).

Bug Fixes: Fixed an issue where players could not toggle between full-width and half-width characters in the Option > X Font settings.