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

:root {
    --bg-body: #f2f5f9;
    --bg-card: #ffffff;
    --text-primary: #0b1a33;
    --text-secondary: #2c3e50;
    --text-muted: #5e6f8d;
    --border-light: #dce2ec;
    --accent: #2563eb;
    --accent-light: #dbeafe;
    --shadow: 0 8px 24px rgba(0, 20, 50, 0.06);
    --radius: 1.25rem;
    --font-base: 1rem;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
    background: var(--bg-body);
    color: var(--text-primary);
    line-height: 1.6;
    padding: 1rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    transition: padding 0.2s;
}

.box {
    width: 100%;
    max-width: 1200px;
    background: var(--bg-card);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 2rem 3rem;
    overflow: hidden;
    transition: all 0.25s ease;
}

.part1 {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: 2rem;
}

.part1-title {
    font-size: 1.8rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.part2 {
    display: flex;
    align-items: center;
    justify-content: space-around;
    flex-wrap: wrap;
    margin-bottom: 2rem;
    gap: 1rem;
}

.tab-item {
    flex: 1;
    min-width: 80px;
    height: 2.75rem;
    font-size: 1rem;
    border-radius: var(--radius);
    background: var(--accent);
    color: rgba(255, 255, 255, 1);
    border: none;
    cursor: pointer;
    transition: all 0.3s ease;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.35);
    padding: 0 1rem;
}

.tab-item:hover {
    background: #1d4ed8;
    transform: translateY(-2px);
}


.tab-item.active {
    background: #1d4ed8;
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(37, 99, 235, 0.5);
}

.part3 {
    background: var(--bg-body);
    border-radius: var(--radius);
    padding: 2rem;
    min-height: 280px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.panel-item {
    display: none;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    animation: fadeIn 0.3s ease;
    width: 100%;
}

.panel-item.active {
    display: flex;
}

.part3 .pic {
    position: relative;
    width: 100%;
    max-width: 400px;
    padding-bottom: 56.25%;
    background: var(--accent);
    border-radius: 0.75rem;
    overflow: hidden;
    margin: 0.5rem 0;
}

.part3 img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: contain;
    display: block;
}

.part3 .content {
    font-size: 1.125rem;
    font-weight: 500;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(12px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===== 响应式 ===== */
@media (max-width: 768px) {
    .box {
        padding: 1.25rem;
    }

    .part1-title {
        font-size: 1.3rem;
    }

    .part2 {
        gap: 0.5rem;
    }

    .tab-item {
        min-width: 60px;
        font-size: 0.85rem;
        height: 2.4rem;
    }

    .part3 {
        padding: 1.5rem;
        min-height: 220px;
    }

    .part3 .pic {
        max-width: 280px;
    }
}

@media (max-width: 480px) {
    .box {
        padding: 1rem;
    }

    .part1-title {
        font-size: 1.1rem;
    }

    .tab-item {
        min-width: 50px;
        font-size: 0.75rem;
        height: 2rem;
        padding: 0 0.5rem;
    }

    .part3 .pic {
        max-width: 200px;
    }
}