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

body {
    font-family: "Microsoft YaHei", sans-serif;
    background-color: #f8f5ff;
    color: #333;
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

:root {
    --primary-color: #6a5acd;
    --secondary-color: #9370db;
    --accent-color: #4b0082;
    --bg-color: #f8f5ff;
    --text-color: #333;
}

.nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: var(--primary-color);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    padding: 12px 15px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
}

.logo img {
    width: 36px;
    height: 36px;
    margin-right: 8px;
    filter: brightness(0) invert(1);
}

.logo span {
    font-size: 32px;
    font-weight: bold;
    color: white;
}

.menu {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 20px;
    padding: 5px;
    border-radius: 4px;
    color: white;
    transition: background 0.3s;
}

.menu:hover {
    background-color: var(--secondary-color);
}

.top-header {
    text-align: center;
    padding: 20px;
    background-color: #f8f8f8;
}

.top-header h1 {
    font-size: 1.5em;
}

.intro-section {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: flex-start;
    padding: 30px 20px;
    gap: 30px;
    margin-top: 60px;
}

.intro-text {
    max-width: 400px;
}

.intro-text h2 {
    font-size: 2em;
    margin-bottom: 10px;
    color: var(--primary-color);
}

.intro-text h3 {
    font-size: 1.6em;
    margin-bottom: 20px;
    color: var(--accent-color);
}

.intro-text p {
    margin-bottom: 10px;
}

.intro-text button {
    background-color: var(--primary-color);
    color: #fff;
    border: none;
    padding: 10px 20px;
    cursor: pointer;
    margin-top: 10px;
    border-radius: 5px;
    transition: background 0.3s;
}

.intro-text button:hover {
    background-color: var(--accent-color);
}

.intro-img img {
    width: 180px;
    height: auto;
    border-radius: 8px;
    border: 4px solid var(--secondary-color);
}

.doing-section {
    text-align: center;
    padding: 30px 20px;
    flex: 1;
}

.doing-section h2 {
    font-size: 1.8em;
    margin-bottom: 10px;
    color: var(--accent-color);
}

.doing-section h3 {
    font-size: 1.4em;
    margin-bottom: 30px;
    color: var(--secondary-color);
}

.cards {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
}

.card {
    width: 260px;
    height: 200px;
    perspective: 1000px;
    margin-bottom: 20px;
    cursor: pointer;
    transition: box-shadow 0.3s ease;
}

.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s;
    transform-style: preserve-3d;
    border-radius: 8px;
    box-shadow: 0 0 5px rgba(0, 0, 0, 0.1);
}

.card:hover,
.card:active {
    box-shadow: 0 0 40px rgba(255, 255, 255, 2);
}

.card-front,
.card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 8px;
    padding: 20px;
    background-color: white;
    color: var(--accent-color);
    border: 1px solid #eee;
}

.card-back {
    transform: rotateY(180deg);
    flex-direction: column;
    text-align: left;
}

.card-front h4 {
    font-size: 1.2em;
    color: var(--primary-color);
}

.card-back p {
    margin-bottom: 8px;
    font-size: 0.9em;
    color: var(--text-color);
}

.footer-section {
    width: 100%;
    background-color: var(--primary-color);
    color: #fff;
}

.footer-bg {
    background-image: linear-gradient(to bottom, var(--primary-color), var(--accent-color));
    background-size: cover;
    background-position: center;
    padding: 30px 20px;
    text-align: center;
    border-radius: 20px 20px 0 0;
    box-shadow: 0 -4px 12px rgba(0, 0, 0, 0.1);
}

button {
    text-decoration: none;
    color: #fff;
    border: none;
    cursor: pointer;
}

button a {
    text-decoration: none;
    color: #fff;
}

@media (max-width: 768px) {
    .nav {
        padding: 10px 12px;
    }

    .logo img {
        width: 32px;
        height: 32px;
    }

    .logo span {
        font-size: 20px;
    }

    .intro-section {
        padding: 20px 15px;
    }

    .intro-text h2 {
        font-size: 1.8em;
    }

    .intro-text h3 {
        font-size: 1.4em;
    }

    .card {
        width: 100%;
        max-width: 260px;
    }
}