/* ==========================================================================
   全提问 (DifferSeek) — 极简主义设计系统 (Minimalist Architecture)
   基于 design-taste-frontend: 纯净单色调、宏观留白、严谨排版、零冗余装饰
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap');

:root {
    --font-sans: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", sans-serif;
    --font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

    --max-width: 1160px;
    --gutter: clamp(20px, 3.5vw, 40px);

    /* 纯净极简黑曜石阶梯 */
    --bg-page: #08090d;
    --bg-surface: #0e1017;
    --bg-surface-elevated: #141722;
    --bg-surface-active: #1a1e2c;

    /* 单一理性点缀色 */
    --accent: #3b82f6;
    --accent-hover: #2563eb;
    --accent-subtle: rgba(59, 130, 246, 0.1);

    /* 精密发丝线 */
    --border: rgba(255, 255, 255, 0.06);
    --border-hover: rgba(255, 255, 255, 0.12);
    --border-accent: rgba(59, 130, 246, 0.3);

    /* 文本色系 */
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-tertiary: #64748b;

    /* 状态指示 */
    --color-match: #10b981;
    --color-diff: #f59e0b;

    /* 极简动效缓动 */
    --transition: 0.18s cubic-bezier(0.16, 1, 0.3, 1);
}

/* ==========================================================================
   Base & Reset
   ========================================================================== */

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: 80px;
    background-color: var(--bg-page);
    color-scheme: dark;
}

body {
    font-family: var(--font-sans);
    background-color: var(--bg-page);
    color: var(--text-primary);
    line-height: 1.65;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    width: 100%;
    max-width: var(--max-width);
    margin-inline: auto;
    padding-inline: var(--gutter);
}

/* ==========================================================================
   Navigation
   ========================================================================== */

.site-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    padding: 16px 0;
    background: rgba(8, 9, 13, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    transition: background var(--transition);
}

.navbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    color: var(--text-primary);
}

.nav-brand img {
    width: 26px;
    height: 26px;
    border-radius: 6px;
}

.nav-brand-text {
    font-size: 15.5px;
    font-weight: 700;
    letter-spacing: -0.02em;
}

.nav-links {
    display: flex;
    align-items: center;
    list-style: none;
    gap: 28px;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 13.5px;
    font-weight: 500;
    transition: color var(--transition);
}

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

.btn-minimal-action {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 7px 16px;
    border-radius: 6px;
    background: #ffffff;
    color: #08090d;
    font-size: 13px;
    font-weight: 650;
    text-decoration: none;
    cursor: pointer;
    transition: all var(--transition);
}

.btn-minimal-action:hover {
    background: #e2e8f0;
    transform: translateY(-1px);
}

.btn-minimal-action:active {
    transform: translateY(0);
}

/* ==========================================================================
   Hero Section
   ========================================================================== */

.hero {
    padding-top: 130px;
    padding-bottom: 80px;
    text-align: center;
}

.hero-status-pill {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 4px 12px;
    border-radius: 6px;
    background: var(--bg-surface);
    border: 1px solid var(--border);
    font-size: 12px;
    color: var(--text-secondary);
    margin-bottom: 28px;
}

.hero-status-pill .indicator {
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--color-match);
}

.hero-title {
    font-size: clamp(2.3rem, 4.8vw, 3.8rem);
    font-weight: 800;
    line-height: 1.15;
    letter-spacing: -0.038em;
    color: #ffffff;
    max-width: 860px;
    margin-inline: auto;
    margin-bottom: 22px;
    text-wrap: balance;
}

.hero-description {
    font-size: clamp(15px, 1.5vw, 17.5px);
    line-height: 1.7;
    color: var(--text-secondary);
    max-width: 640px;
    margin-inline: auto;
    margin-bottom: 34px;
}

.hero-actions {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    gap: 12px;
    margin-bottom: 44px;
}

.btn-hero-primary {
    padding: 12px 24px;
    font-size: 14.5px;
    border-radius: 8px;
}

.hero-trust-bar {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    gap: 16px;
    font-size: 12.5px;
    color: var(--text-tertiary);
    margin-bottom: 54px;
}

.hero-trust-bar a {
    color: var(--text-secondary);
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    transition: color var(--transition);
}

.hero-trust-bar a:hover {
    color: var(--text-primary);
}

/* ==========================================================================
   Minimalist Comparison Matrix
   ========================================================================== */

.comparison-matrix {
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    overflow: hidden;
    text-align: left;
}

.comp-header-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 18px;
    background: var(--bg-surface-elevated);
    border-bottom: 1px solid var(--border);
    font-size: 12.5px;
    color: var(--text-secondary);
}

.comp-tab-selector {
    padding: 12px 18px;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    gap: 8px;
    overflow-x: auto;
}

.comp-tab-btn {
    padding: 5px 12px;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: 5px;
    font-size: 12px;
    font-family: inherit;
    color: var(--text-secondary);
    cursor: pointer;
    white-space: nowrap;
    transition: all var(--transition);
}

.comp-tab-btn:hover,
.comp-tab-btn.is-active {
    background: var(--bg-surface-active);
    border-color: var(--border-hover);
    color: var(--text-primary);
}

.comp-input-row {
    padding: 12px 18px;
    display: flex;
    align-items: center;
    gap: 12px;
    background: var(--bg-page);
    border-bottom: 1px solid var(--border);
}

.comp-input-row input {
    flex: 1;
    background: transparent;
    border: none;
    outline: none;
    color: var(--text-primary);
    font-size: 14px;
    font-family: inherit;
}

.comp-columns-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1px;
    background: var(--border);
}

.comp-column-card {
    background: var(--bg-surface);
    padding: 18px;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.comp-card-head {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 13px;
    font-weight: 650;
    color: var(--text-primary);
    padding-bottom: 10px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.04);
}

.comp-card-head img {
    width: 18px;
    height: 18px;
    border-radius: 4px;
}

.comp-card-text {
    flex: 1;
    font-size: 12.5px;
    line-height: 1.65;
    color: var(--text-secondary);
    font-family: var(--font-mono);
    white-space: pre-wrap;
    min-height: 180px;
}

.comp-card-text mark.match {
    background: rgba(16, 185, 129, 0.12);
    color: #6ee7b7;
    padding: 1px 3px;
    border-radius: 3px;
}

.comp-card-text mark.diff {
    background: rgba(245, 158, 11, 0.12);
    color: #fcd34d;
    padding: 1px 3px;
    border-radius: 3px;
}

/* ==========================================================================
   Feature Highlights
   ========================================================================== */

.section-spacing {
    padding: 96px 0;
}

.section-head {
    margin-bottom: 48px;
}

.section-head h2 {
    font-size: clamp(22px, 2.5vw, 28px);
    font-weight: 750;
    letter-spacing: -0.025em;
    color: #ffffff;
    margin-bottom: 8px;
}

.section-head p {
    font-size: 14.5px;
    color: var(--text-secondary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.feature-item {
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 26px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    transition: border-color var(--transition);
}

.feature-item:hover {
    border-color: var(--border-hover);
}

.feature-item h3 {
    font-size: 16px;
    font-weight: 700;
    color: #ffffff;
}

.feature-item p {
    font-size: 13.5px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ==========================================================================
   Model Wall
   ========================================================================== */

.models-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 12px;
}

.model-card {
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 14px 16px;
    display: flex;
    align-items: center;
    gap: 12px;
    transition: border-color var(--transition), background var(--transition);
}

.model-card:hover {
    border-color: var(--border-hover);
    background: var(--bg-surface-elevated);
}

.model-card img {
    width: 24px;
    height: 24px;
    object-fit: contain;
}

.model-card-info h4 {
    font-size: 13px;
    font-weight: 650;
    color: #ffffff;
}

.model-card-info p {
    font-size: 11.5px;
    color: var(--text-tertiary);
}

/* ==========================================================================
   Privacy & Architecture
   ========================================================================== */

.privacy-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    padding-top: 20px;
}

.privacy-box h4 {
    font-size: 14.5px;
    font-weight: 700;
    color: #ffffff;
    margin-bottom: 6px;
}

.privacy-box p {
    font-size: 13px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ==========================================================================
   FAQ Section
   ========================================================================== */

.faq-split {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 48px;
}

.faq-entries {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.faq-item {
    border-bottom: 1px solid var(--border);
    padding-bottom: 24px;
}

.faq-item:last-child {
    border-bottom: none;
    padding-bottom: 0;
}

.faq-item h4 {
    font-size: 15px;
    font-weight: 700;
    color: #ffffff;
    margin-bottom: 8px;
}

.faq-item p {
    font-size: 13.5px;
    color: var(--text-secondary);
    line-height: 1.65;
}

/* ==========================================================================
   Bottom Action Card
   ========================================================================== */

.bottom-action-card {
    background: var(--bg-surface);
    border: 1px solid var(--border-hover);
    border-radius: 12px;
    padding: 44px 24px;
    text-align: center;
    max-width: 760px;
    margin-inline: auto;
}

.bottom-action-card h2 {
    font-size: 24px;
    font-weight: 750;
    color: #ffffff;
    margin-bottom: 10px;
}

.bottom-action-card p {
    font-size: 14.5px;
    color: var(--text-secondary);
    margin-bottom: 24px;
}

/* ==========================================================================
   Footer
   ========================================================================== */

.site-footer {
    border-top: 1px solid var(--border);
    padding: 36px 0;
    font-size: 12.5px;
    color: var(--text-tertiary);
}

.footer-flex {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 16px;
}

/* ==========================================================================
   Responsive
   ========================================================================== */

@media (max-width: 992px) {
    .features-grid { grid-template-columns: 1fr; }
    .models-grid { grid-template-columns: repeat(3, 1fr); }
    .privacy-grid { grid-template-columns: repeat(2, 1fr); }
    .faq-split { grid-template-columns: 1fr; }
    .comp-columns-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 640px) {
    .nav-links { display: none; }
    .models-grid { grid-template-columns: repeat(2, 1fr); }
    .privacy-grid { grid-template-columns: 1fr; }
    .comp-columns-grid { grid-template-columns: 1fr; }
    .hero { padding-top: 100px; }
}

@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
}