body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f4f7f6;
    color: #333;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}
.container {
    max-width: 600px;
    background: white;
    padding: 40px;
    border-radius: 12px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
    text-align: center;
}
h1 {
    color: #2c3e50;
    margin-bottom: 20px;
}
p {
    line-height: 1.6;
    color: #555;
}
.card {
    background: #eef2f3;
    padding: 20px;
    border-radius: 8px;
    margin: 30px 0;
}
button {
    background-color: #3498db;
    color: white;
    border: none;
    padding: 10px 20px;
    font-size: 16px;
    border-radius: 5px;
    cursor: pointer;
    transition: background 0.3s;
}
button:hover {
    background-color: #2980b9;
}
.hidden {
    display: none;
}
#msg-test {
    margin-top: 15px;
    font-weight: bold;
    color: #27ae60;
}
footer {
    margin-top: 30px;
    font-size: 12px;
    color: #999;
}