/* 基础变量 */
:root {
    --bg: #f8fafc;
    --card: #ffffff;
    --muted: #4b5563;
    --text: #1f2937;
    --brand: #3b82f6;
    --brand-600: #2563eb;
    --brand-700: #1d4ed8;
    --accent: #06b6d4;
    --success: #16a34a;
    --warning: #d97706;
    --danger: #dc2626;
    --shadow: 0 10px 30px rgba(0, 0, 0, .08);
    --radius: 14px;
    --radius-sm: 10px;
    --radius-lg: 24px;
    --container: 1100px;
    --section-alt: #f3f6fb;
    --section-alt-strong: #eaf2ff;
}

* {
    box-sizing: border-box;
}

html,
body {
    height: 100%;
}

body {
    margin: 0;
    font-family: ui-sans-serif, system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 'Noto Sans', 'Apple Color Emoji', 'Segoe UI Emoji';
    color: var(--text);
    background:
        radial-gradient(1200px 800px at 10% -10%, rgba(59, 130, 246, .08), transparent 60%),
        radial-gradient(1000px 700px at 90% 10%, rgba(6, 182, 212, .08), transparent 60%),
        var(--bg);
    line-height: 1.6;
}

img {
    max-width: 100%;
    display: block;
}

a {
    color: inherit;
    text-decoration: none;
}

.container {
    width: 100%;
    max-width: var(--container);
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.site-header {
    position: sticky;
    top: 0;
    z-index: 50;
    background: rgba(255, 255, 255, .85);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(0, 0, 0, .06);
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-weight: 700;
}

.brand-logo {
    font-size: 18px;
}

.brand-text {
    letter-spacing: .2px;
}

.primary-nav {
    display: flex;
    align-items: center;
    gap: 20px;
}

.primary-nav a {
    color: var(--muted);
    padding: 8px 10px;
    border-radius: 8px;
}

.primary-nav a:hover {
    color: var(--text);
    background: rgba(0, 0, 0, .04);
}

/* 顶部预约试听 CTA（浅色主题适配） */
.nav-cta {
    border: 1px solid var(--brand-600);
    color: var(--brand-700);
    background: #ffffff;
    padding: 8px 14px;
    border-radius: 12px;
    box-shadow: 0 2px 8px rgba(37, 99, 235, .12);
}

.nav-cta:hover {
    background: linear-gradient(180deg, var(--brand), var(--brand-600));
    color: #ffffff;
    border-color: transparent;
    box-shadow: 0 6px 16px rgba(37, 99, 235, .25);
}

.nav-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text);
    font-size: 22px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 16px;
    border-radius: 12px;
    border: 1px solid transparent;
    transition: .2s ease;
    font-weight: 600;
}

.btn-primary {
    background: linear-gradient(180deg, var(--brand), var(--brand-600));
    box-shadow: 0 8px 20px rgba(37, 99, 235, .25);
    color: #ffffff;
}

.btn-primary:hover {
    background: linear-gradient(180deg, var(--brand-600), var(--brand-700));
    transform: translateY(-1px);
}

.btn-ghost {
    background: rgba(0, 0, 0, .04);
    border-color: rgba(0, 0, 0, .06);
}

.btn-ghost:hover {
    background: rgba(0, 0, 0, .08);
}

.btn-outline {
    border-color: rgba(0, 0, 0, .16);
    background: transparent;
    color: var(--brand-700);
}

.btn-outline:hover {
    background: rgba(59, 130, 246, .10);
    border-color: var(--brand-600);
}

/* Hero */
.hero {
    display: grid;
    grid-template-columns: 1.2fr 1fr;
    gap: 40px;
    padding: 80px 20px;
    align-items: center;
}

.hero h1 {
    font-size: 38px;
    line-height: 1.2;
    margin: 0 0 10px;
}

.subtitle {
    color: var(--muted);
    margin: 0 0 18px;
}

.hero-cta {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    margin-bottom: 16px;
}

.hero-bullets {
    margin: 10px 0 0;
    padding-left: 20px;
    color: var(--muted);
}

.hero-illustration {
    position: relative;
    height: 320px;
}

.hero-illustration .circle {
    position: absolute;
    inset: 0;
    margin: auto;
    width: 240px;
    height: 240px;
    border-radius: 999px;
    background: radial-gradient(closest-side, rgba(59, 130, 246, .25), rgba(59, 130, 246, .05));
    filter: blur(2px);
}

.hero-illustration .card {
    position: absolute;
    right: 40px;
    top: 40px;
    background: var(--card);
    border: 1px solid rgba(0, 0, 0, .06);
    border-radius: var(--radius);
    padding: 16px 20px;
    box-shadow: var(--shadow);
    font-weight: 700;
    letter-spacing: 2px;
}

/* Sections */
.section {
    padding: 70px 0;
    position: relative;
    z-index: 0;
}

/* 交替背景的分区，增强层次与可读性（全屏宽背景层） */
.section::before {
    content: "";
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    top: 0;
    width: 100vw;
    height: 100%;
    z-index: -1;
    pointer-events: none;
    background: transparent;
}

.section:nth-of-type(even)::before {
    background: linear-gradient(180deg, rgba(255, 255, 255, .70), rgba(255, 255, 255, .70)), var(--section-alt);
}

/* 奇偶模块浅色背景区分（全屏宽） */
.section:nth-of-type(odd)::before {
    background: linear-gradient(180deg, rgba(255, 255, 255, .86), rgba(255, 255, 255, .86)), var(--bg);
}

/* Section 全宽分隔线 */
.section {
    position: relative;
}

.section::after {
    content: "";
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    bottom: 0;
    width: 100vw;
    height: 1px;
    background: rgba(0, 0, 0, .06);
    z-index: 1;
}

main .section:last-of-type::after {
    display: none;
}

.section h2 {
    font-size: 28px;
    margin: 0 0 22px;
    text-align: center;
}

.grid {
    display: grid;
    gap: 18px;
}

.features-grid {
    grid-template-columns: repeat(4, 1fr);
}

.course-grid {
    grid-template-columns: repeat(4, 1fr);
}

.pricing-grid {
    grid-template-columns: repeat(3, 1fr);
    align-items: start;
}

.teacher-grid {
    grid-template-columns: repeat(3, 1fr);
}

.testimonial-grid {
    grid-template-columns: repeat(3, 1fr);
}

.card {
    background: var(--card);
    border: 1px solid rgba(0, 0, 0, .06);
    border-radius: var(--radius);
    padding: 16px;
    box-shadow: var(--shadow);
}

/* 营业执照卡片样式 */
.license-card {
    max-width: 680px;
    margin: 0 auto;
}

.license-card img {
    width: 100%;
    height: auto;
    display: block;
    border-radius: var(--radius-sm);
}

.feature p {
    color: var(--muted);
    margin: 6px 0 0;
}

.course ul,
.price ul {
    margin: 10px 0 0;
    padding-left: 18px;
    color: var(--muted);
}

.price {
    position: relative;
}

.price .price-tag {
    margin: 0;
    color: var(--text);
}

.price .badge {
    position: absolute;
    right: 16px;
    top: -10px;
    background: linear-gradient(90deg, var(--accent), var(--brand));
    color: #ffffff;
    font-weight: 700;
    padding: 4px 10px;
    border-radius: 999px;
    font-size: 12px;
    letter-spacing: .4px;
}

.price.highlight {
    border-color: rgba(59, 130, 246, .35);
    box-shadow: 0 12px 36px rgba(59, 130, 246, .20);
    transform: translateY(-2px);
}

.teacher img {
    width: 100%;
    height: 170px;
    object-fit: cover;
    border-radius: var(--radius-sm);
    margin-bottom: 10px;
}

.teacher-quote {
    color: var(--muted);
    margin: 8px 0 0;
    font-style: italic;
}

.faq-list {
    display: grid;
    gap: 10px;
}

.faq-item {
    background: var(--card);
    border: 1px solid rgba(0, 0, 0, .08);
    border-radius: var(--radius);
    padding: 10px 14px;
}

.faq-item summary {
    cursor: pointer;
    list-style: none;
    position: relative;
    padding-right: 24px;
    font-weight: 600;
}

.faq-item summary::marker {
    display: none;
}

.faq-item[open] {
    border-color: rgba(59, 130, 246, .35);
}

.faq-item .answer {
    color: var(--muted);
    margin-top: 8px;
}

.note {
    color: var(--muted);
    margin-top: 10px;
    font-size: 14px;
}

/* 预约表单（浅色主题） */
form {
    background: #ffffff;
    border: 1px solid rgba(0, 0, 0, .08);
    border-radius: var(--radius-lg);
    padding: 16px;
}

.form-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 14px;
    margin-bottom: 12px;
}

label {
    display: grid;
    gap: 6px;
    font-weight: 600;
    color: var(--text);
}

input,
select,
textarea {
    width: 100%;
    padding: 10px 12px;
    background: #ffffff;
    border: 1px solid rgba(0, 0, 0, .12);
    color: var(--text);
    border-radius: 10px;
    outline: none;
    transition: .15s ease;
}

input:focus,
select:focus,
textarea:focus {
    border-color: rgba(59, 130, 246, .55);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, .18);
}

.form-msg {
    margin-top: 10px;
    font-weight: 600;
}

/* Footer */
.site-footer {
    margin-top: 40px;
    padding: 28px 0 20px;
    border-top: 1px solid rgba(0, 0, 0, .06);
    background: rgba(255, 255, 255, .6);
}

.footer-grid {
    display: grid;
    grid-template-columns: 1.2fr .8fr 1fr;
    gap: 14px;
    align-items: start;
}

.brand-inline {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-weight: 700;
}

.footer-note {
    color: var(--muted);
    margin: 8px 0 0;
}

.footer-nav {
    display: grid;
    grid-template-columns: repeat(3, max-content);
    gap: 8px 12px;
}

.footer-nav a {
    color: var(--muted);
}

.footer-nav a:hover {
    color: var(--text);
}

.footer-contact {
    color: var(--muted);
}

.footer-title {
    margin: 0 0 8px;
    font-size: 16px;
    font-weight: 700;
    color: var(--text);
}

.footer-contact p {
    margin: 4px 0;
}

.footer-contact a {
    color: var(--text);
}

.copyright {
    color: var(--muted);
    font-size: 14px;
    text-align: center;
    padding-top: 12px;
}

/* 响应式 */
@media (max-width: 1024px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .course-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .pricing-grid {
        grid-template-columns: 1fr;
    }

    .teacher-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .testimonial-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .hero {
        grid-template-columns: 1fr;
        padding: 56px 20px;
    }

    .hero h1 {
        font-size: 30px;
    }

    .hero-illustration {
        height: 200px;
    }

    .form-grid {
        grid-template-columns: 1fr;
    }

    .footer-grid {
        grid-template-columns: 1fr;
    }

    .nav-toggle {
        display: inline-block;
    }

    .primary-nav {
        position: absolute;
        right: 20px;
        top: 64px;
        display: none;
        flex-direction: column;
        gap: 8px;
        background: var(--card);
        border: 1px solid rgba(0, 0, 0, .08);
        padding: 12px;
        border-radius: 12px;
        box-shadow: var(--shadow);
    }

    .primary-nav.open {
        display: flex;
    }
}

/* 品牌 Logo 尺寸 */
.brand-img {
    height: 28px;
    width: auto;
    display: block;
}