* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Quicksand', sans-serif;
    background: linear-gradient(-45deg, #ee7752, #e73c7e, #23a6d5, #23d5ab);
    background-size: 400% 400%;
    animation: gradientBG 15s ease infinite;
    color: #fff;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    text-align: center;
    overflow: hidden;
}

@keyframes gradientBG {
    0% {
        background-position: 0% 50%;
    }
    50% {
        background-position: 100% 50%;
    }
    100% {
        background-position: 0% 50%;
    }
}

.container {
    position: relative;
    z-index: 1;
    padding: 2rem;
    background: rgba(0, 0, 0, 0.2);
    border-radius: 15px;
    backdrop-filter: blur(10px);
    box-shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.37);
}

header h1 {
    font-size: 3rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

header p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    font-weight: 400;
}

.countdown {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
}

.time-unit {
    display: flex;
    flex-direction: column;
}

.time-unit span {
    font-size: 4rem;
    font-weight: 600;
    line-height: 1;
}

.time-unit label {
    font-size: 1rem;
    text-transform: uppercase;
    font-weight: 300;
}

/* Hiệu ứng pháo hoa đơn giản */
.fireworks {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url('https://media.giphy.com/media/26tOZ42Mg6pbTUPHW/giphy.gif');
    background-position: center;
    background-size: cover;
    opacity: 0.1;
    z-index: -1;
}

@media (max-width: 600px) {
    header h1 {
        font-size: 2rem;
    }

    header p {
        font-size: 1rem;
    }

    .time-unit span {
        font-size: 2.5rem;
    }

    .time-unit label {
        font-size: 0.8rem;
    }

    .countdown {
        gap: 1rem;
    }
}