I've fixed the search filter error by adding optional chaining (?.) to prevent the toLowerCase() method from being called on undefined values. This ensures that if any city property (name, country, or timezone) is undefined, the filter will safely skip that comparison instead of throwing an error.

I've fixed the mobile responsiveness issues by restructuring the card layout to stack vertically on mobile devices and horizontally on larger screens. The city information now properly wraps and truncates on small screens, time displays are appropriately sized, and slider labels are abbreviated on mobile to prevent overflow while maintaining functionality.