- complete UI overhaul with responsive design and improved styling

- add different hedgehog types: regular, golden and ninja with varying point values
- implement game state management (welcome, game, end screens)
- add combo system with visual feedback and bonus points
- add countdown timer before game starts
- implement pause functionality
- add persistent high score using `localStorage`
- improve mobile support with touch events and viewport meta tag
- add difficulty progression (decreasing mole appearance time)
- replace `sidebar.js` with `logo.js`

Author: TobiasMue91