Improve Difficulty Dropdown UI

Description:

When clicking on the Difficulty dropdown in the Pong Game, the options (Easy, Medium, Hard, etc.) are not clearly visible. Currently, the dropdown options only become visible when hovered over, which makes the UI less intuitive and unattractive for players.

Steps to Reproduce:

- Open the Pong Game.
- Click on the Difficulty dropdown menu.
- Notice that the options are barely visible until hovered.

Current Behavior:

- Dropdown options have poor visibility.
- Players may find it confusing since difficulty levels aren’t clearly displayed.

Expected Behavior:

- Dropdown options should be clearly visible immediately after clicking.
- Options should have a consistent theme and contrast with the background.
- Better styling (hover, active, and focus states) should make the UI more interactive and user-friendly.

Proposed Solution / Enhancements:

- Improve the contrast and background color of dropdown options.
- Use better typography for readability.
- Add hover and focus effects with smooth transitions.
- Ensure dropdown matches the overall modern, glowing theme of the Pong Game.