UI Bug: Dropdown Options Not Clearly Visible in Theme Selector

🎨 UI Bug: Dropdown Options Not Clearly Visible in Theme Selector

Description:
The dropdown menu under the Theme option in the Pong Game UI is not properly styled. The selected option appears, but the dropdown list has:

White background
White or low-contrast text (making it unreadable)
No visible border or shadow separation

Issue Screenshot:

Expected Behavior:
Dropdown options should have sufficient contrast between text and background.
A visible border or subtle shadow should differentiate the dropdown from the background.
All theme options should be easily readable on all screen resolutions.

Steps to Reproduce:
Open the Pong Game.
Navigate to the Theme selector dropdown.
Try selecting a different theme.
Notice that the dropdown list appears blank or hard to read.

Note:
This issue was previously assigned to me. However, due to an accidental deletion of my forked repository, the earlier PR was lost before it could be merged. I'm recreating the issue and will raise a fresh PR for the same.