<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Hello World</title>
<style>
.container {
max-width: 800px;
margin: 0 auto;
padding: 2rem;
}
.btn { background: #3498db; color: white; }
</style>
</head>
<body>
<main class="container">
<h1>Welcome</h1>
<button class="btn" id="greet">Click me</button>
</main>
<script>
document.getElementById('greet').addEventListener('click', () => {
const name = prompt('What is your name?');
alert(`Hello, ${name}!`);
});
</script>
</body>
</html>