/* ============================================================
   HANZISTORY — design system
   Zen cổ điển Á Đông · giấy Tuyên · son triện
   ============================================================ */

:root{
  /* paper & ink */
  --paper:        #faf9f6;
  --paper-2:      #f4f2ec;   /* alt section ground */
  --paper-edge:   #efece4;
  --ink:          #15192100; /* placeholder, overwritten below */
  --ink:          #141a24;   /* near slate-900 */
  --ink-soft:     #334155;
  --slate:        #51596b;
  --slate-2:      #6b7280;
  --line:         #e7e3d9;
  --line-2:       #ddd8cc;

  /* accent — seal red (single accent, ~10-15% area) */
  --seal:         #a8201a;   /* vermilion stamp red */
  --crimson:      #991b1b;   /* deep accent */
  --crimson-700:  #7f1717;
  --crimson-soft: #fbeceb;
  --crimson-line: #f0d6d4;

  /* dark (card backs, final CTA) */
  --night:        #11151d;
  --night-2:      #0c0f15;
  --night-line:   #2a3240;
  --night-text:   #e6e9ef;
  --night-soft:   #9aa3b2;
  --night-rose:   #f0a8a2;   /* soft crimson on dark */

  /* tone colours (muted ink wash — only on thin pinyin underline) */
  --t1:#94a0ad;  --t2:#5a8268;  --t3:#3f6ea8;  --t4:#9168a6;  --t0:#b6b0a4;

  --sans:'Outfit', system-ui, -apple-system, sans-serif;
  --han:'Noto Serif SC', serif;

  --maxw: 1200px;
  --gut: clamp(20px, 5vw, 64px);
  --radius: 14px;
  --shadow-card: 0 24px 60px -34px rgba(20,26,36,.45), 0 6px 18px -12px rgba(20,26,36,.18);
  --shadow-soft: 0 14px 40px -28px rgba(20,26,36,.32);
  --ease: cubic-bezier(.4,0,.2,1);
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
@media (prefers-reduced-motion: reduce){ html{scroll-behavior:auto} }

body{
  font-family:var(--sans);
  background:var(--paper);
  color:var(--ink);
  line-height:1.6;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
  overflow-x:hidden;
}
.han{font-family:var(--han)}
img,svg{display:block;max-width:100%}
a{color:inherit;text-decoration:none}
button{font-family:inherit;cursor:pointer;border:none;background:none}
::selection{background:var(--crimson-soft);color:var(--crimson-700)}

/* ===== Ink-in-water atmosphere (pre-rasterized layers; only transform/opacity animate → GPU-composited, no per-frame filter recompute, no scroll repaint) ===== */
.ink-bg{position:fixed;inset:0;z-index:-1;pointer-events:none;overflow:hidden;contain:strict}
.ink-cloud{
  position:absolute;background-repeat:no-repeat;background-position:center;background-size:contain;
  will-change:transform,opacity;backface-visibility:hidden;transform:translateZ(0);
}
.ink-cloud{background-image:url(../img/ink-cloud.png);width:min(56vmax,720px);height:min(56vmax,720px)}
.ink-cloud--1{top:-13vmax;left:-11vmax;animation:inkBreath 26s ease-in-out infinite alternate}
.ink-cloud--2{bottom:-15vmax;right:-13vmax;width:min(50vmax,640px);height:min(50vmax,640px);animation:inkBreath 32s ease-in-out infinite alternate;animation-delay:-9s}
@keyframes inkBreath{
  0%  {transform:translate3d(0,0,0) scale(.92) rotate(0deg);opacity:.09}
  100%{transform:translate3d(3vmax,2vmax,0) scale(1.22) rotate(5deg);opacity:.16}
}
@media (prefers-reduced-motion: reduce){
  .ink-cloud{animation:none !important;opacity:.13}
}

/* ===== WebGL fluid ink — sống động theo con trỏ ===== */
.fx-fluid{position:fixed;inset:0;width:100vw;height:100vh;z-index:-1;pointer-events:none;display:none}

.section > .wrap, .foot > .wrap{position:relative;z-index:1}

/* ===== Ink ripple on click/tap ===== */
.fx-ripple-ring{
  position:fixed;z-index:70;pointer-events:none;width:150px;height:150px;border-radius:50%;
  border:2px solid rgba(26,22,32,.55);
  box-shadow:0 0 14px rgba(26,22,32,.18), inset 0 0 10px rgba(26,22,32,.14);
  filter:blur(.6px);opacity:0;will-change:transform,opacity;
}
.fx-ripple-dot{
  position:fixed;z-index:70;pointer-events:none;width:22px;height:22px;border-radius:50%;
  background:radial-gradient(circle, rgba(20,16,24,.7), rgba(20,16,24,0) 70%);
  opacity:0;will-change:transform,opacity;
}
@media (prefers-reduced-motion: reduce){
  .fx-ripple-ring,.fx-ripple-dot{display:none}
}

.wrap{max-width:var(--maxw);margin:0 auto;padding-inline:var(--gut)}
.eyebrow{
  display:inline-flex;align-items:center;gap:11px;
  font-size:12.5px;font-weight:600;letter-spacing:.2em;text-transform:uppercase;
  color:var(--crimson);
}
.eyebrow .seal-mini{flex:none}
.quote{font-family:var(--han)}

/* section rhythm */
.section{padding-block:clamp(72px,11vw,140px);position:relative}
.section--alt{background:rgba(244,242,236,0.70)}
.section-head{max-width:680px;margin-bottom:clamp(40px,6vw,72px)}
.section-head.center{margin-inline:auto;text-align:center}
.section-title{
  font-size:clamp(2rem,4.4vw,3.1rem);font-weight:700;letter-spacing:-.025em;
  line-height:1.12;color:var(--ink);
}
.section-title .mark{
  background-image:url("underline.svg");
  background-repeat:no-repeat;background-position:left bottom;background-size:100% .2em;
  padding-bottom:.16em;
  -webkit-box-decoration-break:clone;box-decoration-break:clone;
}
.section-sub{margin-top:18px;font-size:clamp(1rem,1.5vw,1.18rem);color:var(--slate);max-width:60ch;text-wrap:pretty}
.section-head.center .section-sub{margin-inline:auto}

/* buttons */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:10px;
  font-weight:600;font-size:15.5px;line-height:1;letter-spacing:.01em;
  padding:15px 26px;border-radius:11px;
  transition:transform .25s var(--ease), box-shadow .25s var(--ease), background .2s var(--ease);
  white-space:nowrap;
}
.btn--primary{background:var(--crimson);color:#fff;box-shadow:0 12px 26px -14px rgba(153,27,27,.7)}
.btn--primary:hover{background:var(--crimson-700);transform:translateY(-2px);box-shadow:0 18px 34px -14px rgba(153,27,27,.75)}
.btn--ghost{background:transparent;color:var(--ink);border:1.5px solid var(--line-2)}
.btn--ghost:hover{border-color:var(--ink);transform:translateY(-2px)}
.btn--light{background:#fff;color:var(--ink)}
.btn--light:hover{transform:translateY(-2px);box-shadow:var(--shadow-soft)}
.btn--block{width:100%}
.btn:focus-visible{outline:2.5px solid var(--crimson);outline-offset:3px}

/* ===================== NAVBAR ===================== */
.nav{
  position:fixed;inset-block-start:0;inset-inline:0;z-index:80;
  transition:background .35s var(--ease), box-shadow .35s var(--ease), border-color .35s var(--ease);
  border-bottom:1px solid transparent;
}
.nav__inner{
  max-width:var(--maxw);margin:0 auto;padding:18px var(--gut);
  display:flex;align-items:center;justify-content:space-between;gap:24px;
}
.nav.is-stuck{
  background:rgba(250,249,246,.90);
  backdrop-filter:saturate(150%) blur(9px);
  -webkit-backdrop-filter:saturate(150%) blur(9px);
  border-bottom-color:var(--line);
}
.nav.is-stuck .nav__inner{padding-block:13px}
.logo{display:flex;align-items:center;gap:12px}
.logo__seal{width:38px;height:38px;flex:none;transition:width .3s,height .3s}
.logo__word{font-size:21px;font-weight:700;letter-spacing:-.01em;color:var(--ink)}
.logo__word b{color:var(--seal);font-weight:700}

.nav__links{display:flex;align-items:center;gap:6px}
.nav__link{
  font-size:15px;font-weight:500;color:var(--ink-soft);
  padding:9px 14px;border-radius:9px;transition:color .2s,background .2s;
}
.nav__link:hover{color:var(--crimson);background:var(--crimson-soft)}
.nav__right{display:flex;align-items:center;gap:10px}
.nav__signin{font-size:15px;font-weight:600;color:var(--ink-soft);padding:11px 14px;border-radius:9px;transition:color .2s,background .2s}
.nav__signin:hover{color:var(--crimson);background:var(--crimson-soft)}

/* language selector */
.lang{position:relative}
.lang__btn{
  display:inline-flex;align-items:center;gap:8px;
  font-size:14.5px;font-weight:500;color:var(--ink-soft);
  padding:9px 12px;border-radius:9px;border:1px solid transparent;transition:.2s;
}
.lang__btn:hover{background:var(--paper-2);border-color:var(--line)}
.lang__btn .chev{transition:transform .25s var(--ease)}
.lang.is-open .lang__btn .chev{transform:rotate(180deg)}
.lang__menu{
  position:absolute;inset-block-start:calc(100% + 10px);inset-inline-end:0;
  min-width:230px;background:#fff;border:1px solid var(--line);border-radius:14px;
  box-shadow:var(--shadow-card);padding:8px;
  opacity:0;visibility:hidden;transform:translateY(-8px) scale(.98);
  transform-origin:top right;transition:.22s var(--ease);z-index:90;
}
[dir="rtl"] .lang__menu{transform-origin:top left}
.lang.is-open .lang__menu{opacity:1;visibility:visible;transform:none}
.lang__opt{
  display:flex;align-items:center;gap:12px;width:100%;
  padding:10px 12px;border-radius:9px;font-size:14.5px;color:var(--ink-soft);
  text-align:start;transition:background .15s;
}
.lang__opt:hover{background:var(--paper-2)}
.lang__opt .native{font-weight:600;color:var(--ink)}
.lang__opt .en{margin-inline-start:auto;font-size:12px;color:var(--slate-2)}
.lang__opt.is-active{background:var(--crimson-soft)}
.lang__opt.is-active .native{color:var(--crimson)}
.lang__opt .tick{margin-inline-start:auto;color:var(--crimson);opacity:0}
.lang__opt.is-active .tick{opacity:1}
.lang__opt.is-active .en{display:none}

/* hamburger */
.burger{display:none;width:44px;height:44px;border-radius:10px;align-items:center;justify-content:center;color:var(--ink)}
.burger:hover{background:var(--paper-2)}
.burger svg{width:24px;height:24px}

/* mobile sheet */
.msheet{
  position:fixed;inset:0;z-index:95;background:var(--paper);
  display:flex;flex-direction:column;padding:22px var(--gut) 40px;
  transform:translateX(100%);transition:transform .4s var(--ease);visibility:hidden;
}
[dir="rtl"] .msheet{transform:translateX(-100%)}
.msheet.is-open{transform:none;visibility:visible}
.msheet__top{display:flex;align-items:center;justify-content:space-between;margin-bottom:36px}
.msheet__close{width:44px;height:44px;border-radius:10px;display:grid;place-items:center;color:var(--ink)}
.msheet__close:hover{background:var(--paper-2)}
.msheet__links{display:flex;flex-direction:column;gap:4px}
.msheet__links a{font-size:26px;font-weight:600;letter-spacing:-.02em;color:var(--ink);padding:14px 0;border-bottom:1px solid var(--line)}
.msheet__links a .han{color:var(--seal);font-size:24px;margin-inline-end:12px}
.msheet__lang{margin-top:30px}
.msheet__lang h4{font-size:12px;letter-spacing:.16em;text-transform:uppercase;color:var(--slate-2);margin-bottom:12px}
.msheet__lang-grid{display:grid;grid-template-columns:1fr 1fr;gap:8px}
.msheet__lang-grid button{padding:12px 14px;border-radius:10px;border:1px solid var(--line);font-size:15px;font-weight:500;color:var(--ink-soft);text-align:start}
.msheet__lang-grid button.is-active{background:var(--crimson-soft);border-color:var(--crimson-line);color:var(--crimson)}
.msheet__cta{margin-top:auto;padding-top:24px;display:flex;flex-direction:column;gap:10px}

/* ===================== HERO ===================== */
.hero{position:relative;padding-top:clamp(120px,16vw,180px);padding-bottom:clamp(60px,9vw,110px);overflow:hidden}
.hero__brush{position:absolute;inset-block-start:-6%;inset-inline-end:-8%;width:min(60vw,720px);opacity:.05;pointer-events:none;z-index:0;color:var(--ink)}
.hero__grid{position:relative;z-index:1;display:grid;grid-template-columns:1.05fr .95fr;gap:clamp(32px,6vw,80px);align-items:center}
.hero__copy{max-width:620px;display:flex;flex-direction:column;align-items:flex-start}

/* calligraphy brand logotype — stroke-by-stroke brush writing (汉字故事) */
.hero__cn{
  direction:ltr;display:flex;align-items:center;gap:clamp(2px,0.6vw,8px);
  margin-bottom:20px;min-height:96px;margin-inline-start:-4px;
}
.hero__cn .hz{
  width:92px;height:92px;flex:none;display:block;
}
.hero__cn .hz svg{overflow:visible;filter:url(#brush)}
.hero__cn .hz--fallback{
  font-family:var(--han);font-weight:500;font-size:74px;line-height:92px;
  color:#16100d;text-align:center;
}
.hero__cn-seal{
  width:0;height:46px;flex:none;color:var(--seal);overflow:hidden;
  opacity:0;transform:scale(.6) rotate(-6deg);transform-origin:center;
  transition:opacity .5s var(--ease) .1s, transform .5s var(--ease) .1s, width .4s var(--ease);
  align-self:center;margin-inline-start:2px;
}
.hero__cn.is-done .hero__cn-seal{width:46px;opacity:.95;transform:scale(1) rotate(-4deg);margin-inline-start:10px}
@media (prefers-reduced-motion: reduce){
  .hero__cn-seal{transition:none}
}
@media (max-width:620px){
  .hero__cn{min-height:64px;margin-bottom:14px}
  .hero__cn .hz{width:64px;height:64px}
  .hero__cn.is-done .hero__cn-seal{width:34px;height:34px;margin-inline-start:6px}
}
.hero h1{
  font-size:clamp(2.4rem,5.4vw,4.4rem);font-weight:700;letter-spacing:-.035em;
  line-height:1.06;color:var(--ink);margin-top:24px;
}
.hero h1 .em{color:var(--crimson)}
.hero__sub{margin-top:26px;font-size:clamp(1.05rem,1.6vw,1.28rem);color:var(--slate);max-width:48ch;text-wrap:pretty}
.hero__cta{margin-top:38px;display:flex;flex-wrap:wrap;gap:14px}
.hero__meta{margin-top:30px;display:flex;align-items:center;gap:18px;font-size:13.5px;color:var(--slate-2)}
.hero__meta .dot{width:4px;height:4px;border-radius:50%;background:var(--line-2)}
.hero__meta b{color:var(--ink-soft);font-weight:600}

.hero__stage{display:flex;justify-content:center;position:relative}
#heroCard{position:relative;z-index:1;width:100%;max-width:340px}
#heroCard .flip{max-width:none}

/* Ensō (円相) — Zen one-stroke ink ring framing the demo card */
.hero__enso{
  position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);
  width:min(150%,680px);aspect-ratio:1;z-index:0;pointer-events:none;
  opacity:.9;
}
.hero__enso .enso-svg{width:100%;height:100%;overflow:visible;display:block}
[dir="rtl"] .hero__enso{transform:translate(50%,-50%) scaleX(-1)}
@media (max-width:620px){ .hero__enso{display:none} }
.hero__stage::before{
  content:"";position:absolute;width:118%;height:118%;
  background:radial-gradient(ellipse at center, rgba(168,32,26,.05), transparent 62%);
  z-index:0;
}

/* ===================== FLIP CARD ===================== */
.flip{
  position:relative;border:none;background:none;padding:0;
  width:100%;max-width:340px;aspect-ratio:3/4;
  perspective:1600px;cursor:pointer;border-radius:20px;
}
.flip:focus-visible{outline:3px solid var(--crimson);outline-offset:6px}
.flip__inner{
  position:relative;width:100%;height:100%;
  transform-style:preserve-3d;
  transition:transform .7s cubic-bezier(.4,0,.2,1);
}
.flip.is-flipped .flip__inner{transform:rotateY(180deg)}
[dir="rtl"] .flip.is-flipped .flip__inner{transform:rotateY(-180deg)}
@media (hover:hover) and (pointer:fine) and (prefers-reduced-motion: no-preference){
  .flip:hover .flip__inner{transform:rotateY(180deg)}
  [dir="rtl"] .flip:hover .flip__inner{transform:rotateY(-180deg)}
  .flip.is-flipped:hover .flip__inner{transform:rotateY(0deg)}
  [dir="rtl"] .flip.is-flipped:hover .flip__inner{transform:rotateY(0deg)}
}
.flip__face{
  position:absolute;inset:0;backface-visibility:hidden;-webkit-backface-visibility:hidden;
  border-radius:20px;overflow:hidden;display:flex;flex-direction:column;
}
/* FRONT — zen, cream */
.flip__front{
  background:linear-gradient(170deg,#fffefb,#f6f4ee);
  border:1px solid var(--line);box-shadow:var(--shadow-card);
  align-items:center;justify-content:center;padding:26px;text-align:center;
}
.flip__hsk{
  position:absolute;inset-block-start:18px;inset-inline-start:18px;
  font-size:11.5px;font-weight:600;letter-spacing:.04em;color:var(--crimson);
  background:var(--crimson-soft);border:1px solid var(--crimson-line);
  border-radius:999px;padding:4px 11px;
}
.flip__sealwm{position:absolute;inset-block-start:14px;inset-inline-end:14px;width:34px;height:34px;opacity:.9}
.flip__han{font-family:var(--han);font-weight:500;line-height:1;color:var(--ink);
  font-size:clamp(96px,20vw,150px)}
.flip__pin{margin-top:22px;font-size:clamp(20px,3vw,26px);font-weight:500;color:var(--ink-soft)}
.pyin{display:inline-block;border-bottom:3px solid var(--t1);padding-bottom:2px;line-height:1.1}
.pyin[data-tone="1"]{border-color:var(--t1)} .pyin[data-tone="2"]{border-color:var(--t2)}
.pyin[data-tone="3"]{border-color:var(--t3)} .pyin[data-tone="4"]{border-color:var(--t4)}
.pyin[data-tone="0"]{border-color:var(--t0)}
.flip__tools{margin-top:20px;display:flex;align-items:center;gap:14px;justify-content:center}
.spk{
  width:44px;height:44px;border-radius:50%;display:grid;place-items:center;
  border:1px solid var(--line-2);color:var(--ink-soft);background:#fff;transition:.2s;
}
.spk:hover{color:var(--crimson);border-color:var(--crimson-line);background:var(--crimson-soft)}
.spk:focus-visible{outline:2.5px solid var(--crimson);outline-offset:2px}
.flip__hint{
  position:absolute;inset-block-end:18px;inset-inline:0;text-align:center;
  font-size:12.5px;color:var(--slate-2);display:flex;align-items:center;gap:7px;justify-content:center;
}
.flip__hint svg{opacity:.6}

/* BACK — dark slate */
.flip__back{
  background:linear-gradient(165deg,#161b24,#0d1118);
  border:1px solid #222a36;color:var(--night-text);
  transform:rotateY(180deg);
  padding:clamp(16px,4.5%,22px);text-align:start;overflow:hidden;
  display:flex;flex-direction:column;
}
[dir="rtl"] .flip__back{transform:rotateY(-180deg)}
.flip__back-head{display:flex;align-items:baseline;gap:10px;padding-bottom:11px;border-bottom:1px solid var(--night-line);flex:none}
.flip__back-han{font-family:var(--han);font-size:clamp(30px,9%,40px);line-height:1;color:#fff}
.flip__back-pin{font-size:15px;color:var(--night-soft);font-weight:500}
.flip__back-mean{margin-inline-start:auto;font-size:14px;font-weight:600;color:#fff;text-align:end}
.flip__rads{display:flex;gap:7px;margin:12px 0 0;flex:none}
.rad{flex:1;background:rgba(255,255,255,.04);border:1px solid var(--night-line);border-radius:9px;padding:8px 6px;text-align:center}
.rad .rc{font-family:var(--han);font-size:23px;color:#fff;line-height:1}
.rad .rn{margin-top:4px;font-size:10.5px;font-weight:600;letter-spacing:.02em;color:var(--night-rose);line-height:1.2}
.flip__story{font-size:clamp(11.5px,3.7%,13.2px);line-height:1.52;color:#cdd3dd;margin:13px 0 0;flex:1 1 auto;min-height:0;overflow:hidden}
.flip__story em{font-style:normal;font-weight:600;color:var(--night-rose)}
.flip__story .han{font-family:var(--han);color:#fff;font-style:normal}
.flip__compound{margin-top:12px;display:flex;flex-wrap:wrap;gap:7px;flex:none}
.cmp{background:rgba(240,168,162,.1);border:1px solid rgba(240,168,162,.22);border-radius:8px;padding:5px 9px;font-size:12px;color:#f3ddda}
.cmp .han{font-family:var(--han);font-size:15px;color:#fff;margin-inline-end:5px}

/* hero demo card is larger (340px) — scale up & balance its back layout */
#heroCard .flip__back{padding:26px 24px;justify-content:center}
#heroCard .flip__back-head{padding-bottom:16px}
#heroCard .flip__back-han{font-size:46px}
#heroCard .flip__back-pin{font-size:18px}
#heroCard .flip__back-mean{font-size:17px}
/* lone radical (月 is itself the radical) → tidy full-width strip, not a giant square */
#heroCard .flip__rads{margin-top:20px}
#heroCard .flip__rads .rad{display:flex;align-items:center;justify-content:center;gap:12px;padding:14px 16px}
#heroCard .flip__rads .rad .rc{font-size:30px}
#heroCard .flip__rads .rad .rn{margin-top:0;font-size:13.5px}
#heroCard .flip__story{flex:0 0 auto;font-size:16px;line-height:1.6;margin-top:20px}
#heroCard .flip__compound{margin-top:20px;gap:10px}
#heroCard .cmp{padding:8px 13px;font-size:14px}
#heroCard .cmp .han{font-size:18px}

/* reduced motion: crossfade instead of 3D flip */
@media (prefers-reduced-motion: reduce){
  .flip__inner{transition:none}
  .flip.is-flipped .flip__inner,[dir="rtl"] .flip.is-flipped .flip__inner{transform:none}
  .flip__face{backface-visibility:visible;-webkit-backface-visibility:visible;transition:opacity .35s ease}
  .flip__back,[dir="rtl"] .flip__back{transform:none;opacity:0;pointer-events:none}
  .flip__front{opacity:1}
  .flip.is-flipped .flip__front{opacity:0;pointer-events:none}
  .flip.is-flipped .flip__back{opacity:1;pointer-events:auto}
}

/* ===================== HOW IT WORKS ===================== */
.steps{display:grid;grid-template-columns:repeat(4,1fr);gap:clamp(16px,2.5vw,28px);position:relative}
.steps__line{position:absolute;inset-block-start:42px;inset-inline:11%;height:2px;z-index:0;
  background:repeating-linear-gradient(90deg,var(--line-2) 0 7px,transparent 7px 14px)}
[dir="rtl"] .steps__line{transform:scaleX(-1)}
.step{position:relative;z-index:1;text-align:center}
.step__ic{
  width:84px;height:84px;border-radius:18px;margin:0 auto 22px;
  background:#fff;border:1px solid var(--line);box-shadow:var(--shadow-soft);
  display:grid;place-items:center;color:var(--ink);transition:.3s var(--ease);position:relative;
}
.step:hover .step__ic{transform:translateY(-4px);border-color:var(--crimson-line)}
.step__n{position:absolute;inset-block-start:-9px;inset-inline-end:-9px;width:26px;height:26px;border-radius:50%;
  background:var(--crimson);color:#fff;font-size:12.5px;font-weight:600;display:grid;place-items:center}
.step__ic svg{width:42px;height:42px;color:var(--crimson)}
.step h3{font-size:19px;font-weight:600;letter-spacing:-.01em;margin-bottom:8px}
.step p{font-size:14.5px;color:var(--slate);max-width:24ch;margin-inline:auto;text-wrap:pretty}

/* ===================== FLIP LIBRARY GRID ===================== */
.libgrid{display:grid;grid-template-columns:repeat(4,1fr);gap:clamp(16px,2vw,26px)}
.libgrid .flip{max-width:none}
.lib-note{margin-top:34px;display:flex;align-items:center;gap:10px;justify-content:center;font-size:14px;color:var(--slate-2)}
.lib-note .k{font-family:var(--han)}
.kbd{display:inline-grid;place-items:center;min-width:24px;height:24px;padding:0 6px;border:1px solid var(--line-2);border-bottom-width:2px;border-radius:6px;font-size:11px;font-weight:600;color:var(--ink-soft);background:#fff}

/* ===================== WHY / BRAIN ===================== */
.why{display:grid;grid-template-columns:repeat(4,1fr);gap:clamp(18px,2.5vw,26px)}
.why__col{position:relative}
.why__ic{width:54px;height:54px;border-radius:13px;background:#fff;border:1px solid var(--line);
  display:grid;place-items:center;color:var(--crimson);margin-bottom:20px;box-shadow:var(--shadow-soft)}
.why__ic svg{width:28px;height:28px}
.section--alt .why__ic{background:var(--paper)}
.why__col h3{font-size:18px;font-weight:600;letter-spacing:-.01em;margin-bottom:9px;line-height:1.25}
.why__col .sci{display:block;font-size:12px;font-weight:600;letter-spacing:.08em;text-transform:uppercase;color:var(--crimson);margin-bottom:6px}
.why__col p{font-size:14.5px;color:var(--slate);text-wrap:pretty}

/* ===================== FINAL CTA ===================== */
.final{background:var(--night);color:var(--night-text);position:relative;overflow:hidden}
.final__brush{position:absolute;inset-block-end:-20%;inset-inline-start:-6%;width:min(50vw,560px);opacity:.06;color:#fff;pointer-events:none}
.final__wm{position:absolute;inset-block-start:50%;inset-inline-end:4%;transform:translateY(-50%);width:200px;opacity:.07;pointer-events:none}
.final .wrap{position:relative;z-index:1;text-align:center;padding-block:clamp(72px,11vw,128px)}
.final .eyebrow{color:var(--night-rose)}
.final h2{font-size:clamp(2rem,4.6vw,3.3rem);font-weight:700;letter-spacing:-.025em;line-height:1.1;margin:18px auto 0;max-width:18ch;color:#fff}
.final h2 .free{
  color:var(--night-rose);
  background-image:url("underline.svg");
  background-repeat:no-repeat;background-position:left bottom;background-size:100% .19em;
  padding-bottom:.14em;
  -webkit-box-decoration-break:clone;box-decoration-break:clone;
}
.final__sub{margin:22px auto 0;font-size:clamp(1rem,1.5vw,1.18rem);color:var(--night-soft);max-width:46ch}
.final__form{margin:38px auto 0;max-width:480px;display:flex;flex-direction:column;gap:12px}
.final__row{display:flex;gap:10px}
.final__input{
  flex:1;background:rgba(255,255,255,.06);border:1px solid var(--night-line);
  border-radius:11px;padding:15px 18px;color:#fff;font-size:15.5px;font-family:inherit;transition:.2s;
}
.final__input::placeholder{color:#6f7888}
.final__input:focus{outline:none;border-color:var(--night-rose);background:rgba(255,255,255,.09)}
.final__or{display:flex;align-items:center;gap:14px;color:var(--night-soft);font-size:13px;margin:4px 0}
.final__or::before,.final__or::after{content:"";flex:1;height:1px;background:var(--night-line)}
.btn--google{background:#fff;color:#1f2430;border:1px solid #fff}
.btn--google:hover{background:#f1f1f1}
.final__fine{margin-top:18px;font-size:12.5px;color:#6f7888}
.final__msg{font-size:14px;color:var(--night-rose);min-height:20px;font-weight:500}

/* ===================== FOOTER ===================== */
.foot{background:rgba(244,242,236,0.78);border-top:1px solid var(--line);padding-block:clamp(56px,8vw,84px) 36px}
.foot__grid{display:grid;grid-template-columns:1.6fr 1fr 1fr;gap:clamp(28px,5vw,64px)}
.foot__brand .logo{margin-bottom:18px}
.foot__brand p{font-size:14.5px;color:var(--slate);max-width:34ch;text-wrap:pretty}
.foot__col h4{font-size:12px;letter-spacing:.14em;text-transform:uppercase;color:var(--slate-2);font-weight:600;margin-bottom:18px}
.foot__col ul{list-style:none;display:flex;flex-direction:column;gap:11px}
.foot__col a{font-size:15px;color:var(--ink-soft);transition:color .2s;display:inline-flex;align-items:center;gap:8px}
.foot__col a:hover{color:var(--crimson)}
.foot__col .soon{font-size:10.5px;font-weight:600;letter-spacing:.04em;color:var(--slate-2);border:1px solid var(--line-2);border-radius:999px;padding:2px 7px}
.foot__bottom{margin-top:clamp(40px,6vw,64px);padding-top:26px;border-top:1px solid var(--line);
  display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap}
.foot__bottom p{font-size:13.5px;color:var(--slate-2)}
.foot__legal{display:flex;gap:22px}
.foot__legal a{font-size:13.5px;color:var(--slate-2)}
.foot__legal a:hover{color:var(--crimson)}

/* ===================== RESPONSIVE ===================== */
@media (max-width:1000px){
  .hero__grid{grid-template-columns:1fr;gap:48px}
  .hero__copy{max-width:none;text-align:center;margin-inline:auto;align-items:center}
  .hero__cta,.hero__meta{justify-content:center}
  .hero__brush{opacity:.04}
  .libgrid{grid-template-columns:1fr 1fr}
  .why{grid-template-columns:1fr 1fr;gap:34px 26px}
}
@media (max-width:860px){
  .nav__links{display:none}
  .nav .lang{display:none}
  .nav__right .btn{display:none}
  .nav__signin{display:none}
  .burger{display:flex}
  .steps{grid-template-columns:1fr 1fr;gap:40px 24px}
  .steps__line{display:none}
}
@media (max-width:620px){
  .libgrid{grid-template-columns:1fr;max-width:360px;margin-inline:auto}
  .why{grid-template-columns:1fr;gap:30px}
  .foot__grid{grid-template-columns:1fr;gap:40px}
  .final__row{flex-direction:column}
  .hero h1{font-size:clamp(2.1rem,9vw,3rem)}
  .flip__han{font-size:clamp(72px,26vw,110px)}
}