Refactor Game Functions to Modern ES6+ Syntax (Arrow Functions & Destructuring)

I will refactor the core game functions in script.js to use modern ES6+ JavaScript syntax. Specifically, the `resetBall` and `drawRoundedRect` functions will be converted from traditional function declarations to arrow functions, and destructuring is used to extract properties from objects.

#### Benefits
- **Readability:** Arrow functions are more concise and visually distinct, making the code easier to read and understand.
- **Consistency:** Using ES6+ syntax aligns the codebase with modern JavaScript standards, which is expected by most contributors.
- **Reduced Errors:** Destructuring helps prevent mistakes by extracting only the needed properties, making code intentions clearer.
- **Contributor-Friendly:** New contributors are more likely to be familiar with ES6+ syntax, lowering the barrier to entry and making collaboration smoother.
- **Maintainability:** Modern syntax and clear structure make future updates and bug fixes easier to implement.
- **Performance:** While the performance impact is minor, modern syntax can sometimes be optimized better by JavaScript engines.

This refactor supports the project's commitment to clean, modern, and maintainable code, as outlined in the contributing guidelines. It also helps make the project more welcoming and easier to work with for open-source contributors.