/* ============================================
   KEXIN BIO · CASE PAGE DESIGN SYSTEM
   与主页面共享视觉语言，但为案例页做了定制
   ============================================ */

:root {
    /* Surfaces */
    --bg-black: #000000;
    --bg-charcoal: #0a0a0a;
    --bg-graphite: #161617;
    --bg-elevated: #1d1d1f;
    --bg-silver: #f5f5f7;
    --bg-silver-2: #fbfbfd;
    --bg-pure: #ffffff;

    /* Text on dark */
    --text-on-dark-1: #f5f5f7;
    --text-on-dark-2: #a1a1a6;
    --text-on-dark-3: #6e6e73;

    /* Text on light */
    --text-on-light-1: #1d1d1f;
    --text-on-light-2: #424245;
    --text-on-light-3: #6e6e73;

    --border-on-dark: rgba(255, 255, 255, 0.08);
    --border-on-dark-strong: rgba(255, 255, 255, 0.16);
    --border-on-light: rgba(0, 0, 0, 0.08);

    /* Single accent — Apple 黑白灰 */
    --accent: #1d1d1f;
    --accent-on-dark: #f5f5f7;
    --accent-soft: rgba(29, 29, 31, 0.06);
    --accent-soft-strong: rgba(29, 29, 31, 0.10);
    --accent-glow: rgba(29, 29, 31, 0.20);
    /* legacy aliases (kept so existing rules resolve) */
    --accent-1: var(--accent);
    --accent-2: var(--accent);
    --accent-3: var(--accent);
    --accent-4: var(--accent);
    --accent-gradient: var(--accent);
    --accent-gradient-soft: var(--accent-soft);
    --accent-gradient-text: var(--accent);

    --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text", "PingFang SC", "Helvetica Neue", "Microsoft YaHei", sans-serif;
    --font-display: "SF Pro Display", -apple-system, BlinkMacSystemFont, "PingFang SC", "Helvetica Neue", sans-serif;

    --s-1: 0.5rem;
    --s-2: 1rem;
    --s-3: 1.5rem;
    --s-4: 2rem;
    --s-5: 3rem;
    --s-6: 4rem;
    --s-8: 6rem;
    --s-10: 8rem;
    --s-12: 10rem;
    --s-16: 14rem;

    --r-sm: 10px;
    --r-md: 18px;
    --r-lg: 24px;
    --r-xl: 32px;
    --r-2xl: 40px;
    --r-full: 9999px;

    --blur-glass: saturate(180%) blur(20px);
    --shadow-card-light: 0 1px 2px rgba(0,0,0,0.04), 0 8px 24px rgba(0,0,0,0.06);
    --shadow-card-light-hover: 0 4px 12px rgba(0,0,0,0.06), 0 24px 60px rgba(0,0,0,0.10);
    --shadow-card-dark: 0 1px 2px rgba(0,0,0,0.2), 0 8px 24px rgba(0,0,0,0.3);

    --container: 1200px;
    --container-narrow: 920px;
}

*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
    font-family: var(--font-sans);
    font-size: 17px;
    line-height: 1.47;
    color: var(--text-on-light-1);
    background: var(--bg-silver);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}
img, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; cursor: pointer; border: none; background: none; }
ul, ol { list-style: none; }
::selection { background: rgba(94, 94, 255, 0.3); color: #fff; }

.container {
    width: 100%;
    max-width: var(--container);
    margin: 0 auto;
    padding-left: clamp(1.25rem, 4vw, 2.5rem);
    padding-right: clamp(1.25rem, 4vw, 2.5rem);
}
.container-narrow {
    width: 100%;
    max-width: var(--container-narrow);
    margin: 0 auto;
    padding-left: clamp(1.25rem, 4vw, 2.5rem);
    padding-right: clamp(1.25rem, 4vw, 2.5rem);
}

/* Typography */
.eyebrow {
    display: inline-block;
    font-size: 0.8125rem;
    font-weight: 600;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--text-on-light-2);
    margin-bottom: var(--s-3);
}
.eyebrow.on-dark { color: var(--accent-on-dark); }
.display-1 {
    font-family: var(--font-display);
    font-size: clamp(2.75rem, 6.5vw, 5.5rem);
    font-weight: 600;
    line-height: 1.05;
    letter-spacing: -0.035em;
}
.display-2 {
    font-family: var(--font-display);
    font-size: clamp(2.25rem, 4.8vw, 4rem);
    font-weight: 600;
    line-height: 1.08;
    letter-spacing: -0.03em;
}
.display-3 {
    font-family: var(--font-display);
    font-size: clamp(1.75rem, 3vw, 2.5rem);
    font-weight: 600;
    line-height: 1.15;
    letter-spacing: -0.02em;
}
.gradient-text {
    background: var(--accent-gradient-text);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    color: transparent;
}
.lead {
    font-size: clamp(1.125rem, 1.6vw, 1.375rem);
    line-height: 1.45;
    color: var(--text-on-light-2);
    font-weight: 400;
    letter-spacing: -0.005em;
}
.lead.on-dark { color: var(--text-on-dark-2); }

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.4em;
    padding: 0.85em 1.5em;
    font-size: 1rem;
    font-weight: 500;
    letter-spacing: -0.01em;
    border-radius: var(--r-full);
    transition: transform 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94),
                background-color 0.25s ease,
                color 0.25s ease,
                box-shadow 0.3s ease;
    white-space: nowrap;
    cursor: pointer;
}
.btn-primary {
    background: var(--accent-2);
    color: #fff;
}
.btn-primary:hover {
    background: #2c2c2e;
    transform: translateY(-1px);
}
.btn-on-dark-primary {
    background: #fff;
    color: #000;
}
.btn-on-dark-primary:hover {
    background: rgba(255,255,255,0.92);
    transform: translateY(-1px);
}
.btn-on-dark-ghost {
    color: #fff;
    border: 1px solid var(--border-on-dark-strong);
}
.btn-on-dark-ghost:hover {
    background: rgba(255,255,255,0.08);
    transform: translateY(-1px);
}

/* ============================================
   NAV
   ============================================ */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(0, 0, 0, 0.72);
    backdrop-filter: var(--blur-glass);
    -webkit-backdrop-filter: var(--blur-glass);
    border-bottom: 1px solid var(--border-on-dark);
    transition: background 0.3s ease, border-color 0.3s ease;
}
.nav-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 56px;
}
.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.625rem;
    color: var(--text-on-dark-1);
}
.nav-brand img {
    width: 30px;
    height: 30px;
    border-radius: 7px;
}
.nav-brand-text {
    font-size: 0.95rem;
    font-weight: 600;
    letter-spacing: -0.01em;
}
.nav-brand-text .sub {
    color: var(--text-on-dark-2);
    font-weight: 400;
    margin-left: 0.25rem;
}
.nav-links {
    display: flex;
    align-items: center;
    gap: 2rem;
}
.nav-links a {
    font-size: 0.875rem;
    color: var(--text-on-dark-2);
    transition: color 0.2s ease;
    font-weight: 400;
}
.nav-links a:hover { color: var(--text-on-dark-1); }
.nav-cta {
    font-size: 0.875rem;
    color: var(--text-on-dark-1);
    background: rgba(255,255,255,0.1);
    padding: 0.45rem 0.95rem;
    border-radius: var(--r-full);
    border: 1px solid var(--border-on-dark-strong);
    transition: all 0.2s ease;
}
.nav-cta:hover {
    background: rgba(255,255,255,0.16);
    transform: translateY(-1px);
}

/* ============================================
   CASE HERO
   ============================================ */
.case-hero {
    position: relative;
    background: var(--bg-black);
    color: var(--text-on-dark-1);
    padding: calc(56px + var(--s-12)) 0 var(--s-12);
    overflow: hidden;
    isolation: isolate;
}
.case-hero::before {
    content: '';
    position: absolute;
    inset: 0;
    z-index: -1;
    background:
        radial-gradient(ellipse 60% 50% at 20% 30%, rgba(0, 145, 255, 0.18) 0%, transparent 60%),
        radial-gradient(ellipse 50% 50% at 80% 20%, rgba(176, 97, 255, 0.18) 0%, transparent 60%),
        radial-gradient(ellipse 70% 50% at 50% 100%, rgba(0, 212, 255, 0.12) 0%, transparent 60%);
    animation: meshShift 18s ease-in-out infinite alternate;
}
@keyframes meshShift {
    0%   { transform: translate3d(0,0,0) scale(1); }
    50%  { transform: translate3d(-2%, 1%, 0) scale(1.05); }
    100% { transform: translate3d(2%, -1%, 0) scale(1.02); }
}
.case-hero .container-narrow { position: relative; }
.case-hero .industry {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.8125rem;
    font-weight: 600;
    letter-spacing: 0.04em;
    color: var(--text-on-dark-1);
    background: rgba(255,255,255,0.08);
    border: 1px solid var(--border-on-dark-strong);
    padding: 0.5rem 1rem;
    border-radius: var(--r-full);
    margin-bottom: var(--s-4);
}
.case-hero .industry .dot {
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent-on-dark);
    box-shadow: 0 0 8px var(--accent-on-dark);
}
.case-hero h1 {
    font-family: var(--font-display);
    font-size: clamp(2.5rem, 5.5vw, 4.5rem);
    font-weight: 600;
    line-height: 1.05;
    letter-spacing: -0.035em;
    margin-bottom: var(--s-3);
    max-width: 18ch;
}
.case-hero .lead {
    max-width: 60ch;
    color: var(--text-on-dark-2);
}
.case-hero .meta {
    display: flex;
    gap: 2rem;
    margin-top: var(--s-6);
    padding-top: var(--s-4);
    border-top: 1px solid var(--border-on-dark);
    flex-wrap: wrap;
}
.case-hero .meta-item .label {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    color: var(--text-on-dark-3);
    margin-bottom: 0.4rem;
}
.case-hero .meta-item .value {
    font-size: 0.95rem;
    color: var(--text-on-dark-1);
    font-weight: 500;
}

/* ============================================
   CASE CONTENT
   ============================================ */
.case-content {
    padding: var(--s-12) 0;
}
.case-block {
    background: var(--bg-pure);
    border-radius: var(--r-2xl);
    padding: clamp(2rem, 4vw, 3rem);
    border: 1px solid var(--border-on-light);
    margin-bottom: 1.5rem;
    transition: box-shadow 0.3s ease, transform 0.3s ease;
}
.case-block:hover {
    box-shadow: var(--shadow-card-light);
}
.case-block-head {
    display: flex;
    align-items: center;
    gap: 0.875rem;
    margin-bottom: var(--s-4);
}
.case-block-head .icon {
    width: 44px;
    height: 44px;
    border-radius: 12px;
    background: var(--accent-gradient-soft);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--accent-2);
    flex-shrink: 0;
}
.case-block-head .icon svg { width: 24px; height: 24px; }
.case-block-head h2 {
    font-size: clamp(1.375rem, 2.4vw, 1.75rem);
    font-weight: 600;
    letter-spacing: -0.025em;
    color: var(--text-on-light-1);
}

/* Comparison */
.comparison {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
}
.comparison-side {
    padding: 1.75rem;
    border-radius: var(--r-lg);
    border: 1px solid var(--border-on-light);
    background: var(--bg-silver);
}
.comparison-side.after {
    background: var(--bg-pure);
}
.comparison-side h3 {
    font-size: 0.95rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-on-light-1);
}
.comparison-side ul li {
    padding: 0.65rem 0 0.65rem 1.75rem;
    position: relative;
    color: var(--text-on-light-2);
    font-size: 0.95rem;
    line-height: 1.5;
}
.comparison-side ul li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0.95rem;
    width: 8px;
    height: 1.5px;
    background: var(--text-on-light-1);
    border-radius: 2px;
}
.comparison-side ul li::after {
    content: '';
    position: absolute;
    left: 0;
    top: 0.7rem;
    width: 12px;
    height: 12px;
    border: 1.5px solid var(--text-on-light-1);
    border-radius: 50%;
    border-top-color: transparent;
    border-right-color: transparent;
    transform: rotate(45deg);
    background: transparent;
}
.comparison-side.after ul li::before { display: none; }
.comparison-side.after ul li::after {
    content: '';
    position: absolute;
    left: 0;
    top: 0.9rem;
    width: 16px;
    height: 8px;
    border-left: 2px solid var(--text-on-light-1);
    border-bottom: 2px solid var(--text-on-light-1);
    transform: rotate(-45deg);
    border-radius: 0;
    border-top-color: transparent;
    border-right-color: transparent;
    background: transparent;
    width: 8px;
    height: 14px;
}

/* Benefits grid */
.benefits-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
}
.benefit-card {
    background: var(--bg-silver);
    border-radius: var(--r-lg);
    padding: 1.5rem;
    transition: all 0.3s ease;
    border: 1px solid transparent;
}
.benefit-card:hover {
    background: var(--bg-pure);
    border-color: var(--border-on-light);
    transform: translateY(-2px);
    box-shadow: var(--shadow-card-light);
}
.benefit-card h4 {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text-on-light-1);
    margin-bottom: 0.5rem;
    letter-spacing: -0.015em;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}
.benefit-card h4 .emoji {
    font-size: 1.2rem;
    line-height: 1;
}
.benefit-card p {
    color: var(--text-on-light-2);
    font-size: 0.9rem;
    line-height: 1.55;
}

/* Stats */
.stats-row {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
    margin-bottom: 1.5rem;
}
.stat-box {
    background: var(--bg-black);
    border-radius: var(--r-lg);
    padding: 2rem 1.5rem;
    text-align: center;
    color: #fff;
    position: relative;
    overflow: hidden;
    isolation: isolate;
}
.stat-box::after {
    content: '';
    position: absolute;
    inset: 0;
    z-index: -1;
    background: radial-gradient(ellipse at top right, rgba(255,255,255,0.08), transparent 60%);
}
.stat-box .n {
    font-family: var(--font-display);
    font-size: clamp(2.25rem, 4vw, 3rem);
    font-weight: 600;
    letter-spacing: -0.035em;
    line-height: 1;
    color: #fff;
    margin-bottom: 0.4rem;
}
.stat-box .l {
    font-size: 0.875rem;
    color: rgba(255,255,255,0.7);
    letter-spacing: -0.005em;
}

/* Outcome grid (after stats) */
.outcome-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin-top: 1.5rem;
}

/* ============================================
   CASE CTA
   ============================================ */
.case-cta {
    background: var(--bg-black);
    color: var(--text-on-dark-1);
    text-align: center;
    padding: var(--s-12) 0;
    position: relative;
    overflow: hidden;
    isolation: isolate;
}
.case-cta::before {
    content: '';
    position: absolute;
    inset: 0;
    z-index: -1;
    background: radial-gradient(ellipse 50% 50% at 50% 50%, rgba(94, 94, 255, 0.18) 0%, transparent 60%);
}
.case-cta h2 {
    font-family: var(--font-display);
    font-size: clamp(2.25rem, 4.5vw, 3.5rem);
    font-weight: 600;
    line-height: 1.08;
    letter-spacing: -0.03em;
    margin-bottom: var(--s-3);
    max-width: 18ch;
    margin-left: auto;
    margin-right: auto;
}
.case-cta .lead {
    color: var(--text-on-dark-2);
    max-width: 48ch;
    margin: 0 auto var(--s-5);
}
.case-cta-actions {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* Back link */
.back-link {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--text-on-light-2);
    font-size: 0.9rem;
    font-weight: 500;
    margin-bottom: var(--s-4);
    transition: color 0.2s ease;
}
.back-link:hover { color: var(--accent); }
.back-link svg { width: 14px; height: 14px; transition: transform 0.2s ease; }
.back-link:hover svg { transform: translateX(-2px); }

/* ============================================
   FOOTER
   ============================================ */
footer {
    background: var(--bg-black);
    color: var(--text-on-dark-3);
    padding: 2.5rem 0;
    border-top: 1px solid var(--border-on-dark);
}
.footer-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}
.footer-brand {
    display: flex;
    align-items: center;
    gap: 0.625rem;
    color: var(--text-on-dark-2);
    font-size: 0.875rem;
}
.footer-brand img { width: 24px; height: 24px; border-radius: 6px; }
.footer-meta {
    font-size: 0.8125rem;
    color: var(--text-on-dark-3);
}

/* ============================================
   REVEAL ANIMATIONS
   ============================================ */
.reveal {
    opacity: 0;
    transform: translateY(28px);
    transition: opacity 0.9s cubic-bezier(0.25, 0.46, 0.45, 0.94),
                transform 0.9s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    will-change: opacity, transform;
}
.reveal.is-visible {
    opacity: 1;
    transform: translateY(0);
}
.reveal-stagger > * {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.7s ease, transform 0.7s ease;
}
.reveal-stagger.is-visible > * { opacity: 1; transform: translateY(0); }
.reveal-stagger.is-visible > *:nth-child(1) { transition-delay: 0.05s; }
.reveal-stagger.is-visible > *:nth-child(2) { transition-delay: 0.12s; }
.reveal-stagger.is-visible > *:nth-child(3) { transition-delay: 0.19s; }
.reveal-stagger.is-visible > *:nth-child(4) { transition-delay: 0.26s; }
.reveal-stagger.is-visible > *:nth-child(5) { transition-delay: 0.33s; }
.reveal-stagger.is-visible > *:nth-child(6) { transition-delay: 0.40s; }

@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
    .reveal, .reveal-stagger > * { opacity: 1 !important; transform: none !important; }
}

/* ============================================
   RESPONSIVE
   ============================================ */
@media (max-width: 768px) {
    .nav-links { display: none; }
    .comparison { grid-template-columns: 1fr; }
    .benefits-grid { grid-template-columns: 1fr; }
    .stats-row { grid-template-columns: 1fr; }
    .outcome-grid { grid-template-columns: 1fr; }
    .case-block { padding: 1.5rem; }
    .case-hero .meta { gap: 1.25rem; }
    .case-content { padding: var(--s-10) 0; }
    .case-cta { padding: var(--s-10) 0; }
}