body {
    font-family: Arial, sans-serif;
    text-align: center;
    background-color: #f8f8f8;
    margin: 0;
    padding: 0;
}

.container {
    margin-top: 50px;
    padding: 20px;
}

h1 {
    color: #6a0dad;
    font-size: 32px;
    font-weight: bold;
    margin-bottom: 20px;
}

/* Đếm ngược */
#countdown {
    font-size: 48px; /* Mặc định to */
    font-weight: bold;
    color: #d9534f;
    margin: 20px 0;
    background: #fff3cd; /* Nền vàng nhạt */
    padding: 20px;
    border-radius: 10px;
    display: inline-block;
    box-shadow: 0px 0px 10px rgba(0, 0, 0, 0.2);
    width: fit-content;
}

/* Ảnh */
.image {
    width: 100%;
    max-width: 300px;
    display: block;
    margin: 20px auto;
    border-radius: 10px;
    transition: transform 0.3s ease-in-out;
}

/* Nút đăng ký */
.button {
    display: inline-block;
    margin-top: 20px;
    text-decoration: none;
    background: linear-gradient(45deg, #ff6b6b, #ff4757);
    color: white;
    padding: 15px 30px;
    border-radius: 10px;
    font-size: 24px;
    font-weight: bold;
    box-shadow: 0px 5px 15px rgba(255, 0, 0, 0.3);
    transition: 0.3s;
}

.button:hover {
    background: linear-gradient(45deg, #ff4757, #ff6b6b);
    transform: scale(1.1);
}

/* RESPONSIVE */
@media (max-width: 768px) {
    h1 {
        font-size: 24px;
    }

    #countdown {
        font-size: 32px;
        padding: 15px;
    }

    .button {
        font-size: 20px;
        padding: 12px 25px;
    }
}

@media (max-width: 480px) {
    h1 {
        font-size: 20px;
    }

    #countdown {
        font-size: 24px;
        padding: 10px;
    }

    .button {
        font-size: 18px;
        padding: 10px 20px;
    }
}

@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.05); } /* Phồng lên 5% */
    100% { transform: scale(1); }
}