/* ============ HanziCards — ink & rice-paper aesthetic ============ */
:root {
  --paper: #f6f1e7;
  --paper-deep: #efe7d7;
  --ink: #26221c;
  --ink-soft: #5b5345;
  --vermilion: #b03a2e;
  --vermilion-deep: #8e2d23;
  --gold: #b8860b;
  --card-front: #fffdf7;
  --card-back: #2d2924;
  --serif-zh: "Noto Serif SC", "Songti SC", "SimSun", serif;
  --serif-en: "Spectral", Georgia, serif;
  --serif-py: "Noto Serif", "Segoe UI", Georgia, serif; /* full pinyin diacritics (ǎ ǒ ǐ ǚ) */
  --radius: 14px;
  --shadow: 0 2px 6px rgba(38,34,28,.08), 0 12px 32px rgba(38,34,28,.10);
}

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

body {
  font-family: var(--serif-en);
  background: var(--paper);
  background-image: radial-gradient(circle at 18% 12%, rgba(184,134,11,.05), transparent 40%),
                    radial-gradient(circle at 85% 90%, rgba(176,58,46,.04), transparent 45%);
  color: var(--ink);
  line-height: 1.6;
}

.zh { font-family: var(--serif-zh); }

/* ---------- header ---------- */
.site-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 1.4rem clamp(1.2rem, 5vw, 4rem);
  border-bottom: 1px solid rgba(38,34,28,.12);
}
.brand { display: flex; align-items: center; gap: 1rem; }
.seal {
  font-family: var(--serif-zh); font-weight: 900;
  background: var(--vermilion); color: #fdf6ec;
  width: 3.4rem; height: 3.4rem; border-radius: 8px;
  display: grid; place-items: center;
  font-size: 1.05rem; line-height: 1.15; text-align: center;
  box-shadow: inset 0 0 0 2px rgba(253,246,236,.35), 0 3px 8px rgba(142,45,35,.35);
}
.brand-text h1 { font-size: 1.5rem; letter-spacing: .02em; }
.tagline { font-size: .85rem; color: var(--ink-soft); font-family: var(--serif-zh); }
.top-nav a {
  color: var(--ink-soft); text-decoration: none; margin-left: 1.4rem;
  font-size: .9rem; border-bottom: 2px solid transparent; padding-bottom: 2px;
  transition: color .2s, border-color .2s;
}
.top-nav a:hover { color: var(--vermilion); border-color: var(--vermilion); }

/* ---------- hero ---------- */
.hero { padding: clamp(3rem, 8vw, 6rem) clamp(1.2rem, 5vw, 4rem) clamp(2rem, 5vw, 4rem); }
.hero-inner { max-width: 860px; }
.hero h2 {
  font-size: clamp(1.9rem, 4.5vw, 3.2rem);
  font-weight: 600; line-height: 1.2; margin-bottom: .5rem;
}
.hero h2 em { font-style: italic; }
.hero-zh {
  font-family: var(--serif-zh); font-size: clamp(1.1rem, 2.2vw, 1.5rem);
  color: var(--vermilion); margin-bottom: 1.6rem; letter-spacing: .12em;
}
.hero-body { max-width: 640px; font-size: 1.05rem; margin-bottom: 1.4rem; }
.hero-stats {
  max-width: 640px; font-size: .95rem; color: var(--ink-soft);
  border-left: 3px solid var(--gold); padding-left: 1rem;
}
.hero-stats .zh { display: block; font-size: .85rem; margin-top: .3rem; }

/* ---------- sections ---------- */
.section-title {
  display: flex; flex-direction: column; gap: .2rem;
  font-size: clamp(1.5rem, 3vw, 2.1rem); font-weight: 600;
  margin-bottom: 1rem;
}
.section-title .zh { font-size: .9rem; color: var(--vermilion); letter-spacing: .25em; font-weight: 400; }

.how { padding: clamp(2rem, 6vw, 4rem) clamp(1.2rem, 5vw, 4rem); background: var(--paper-deep); }
.demo-caption { font-size: .92rem; color: var(--ink-soft); margin: 1.2rem 0 .9rem; }

/* evolution demo row */
.evo-row {
  display: flex; align-items: stretch; gap: .4rem; flex-wrap: wrap;
}
.evo-stage {
  background: var(--card-front); border-radius: var(--radius);
  padding: 1rem .9rem .8rem; text-align: center; flex: 1 1 120px; max-width: 170px;
  box-shadow: var(--shadow); position: relative;
}
.evo-stage .glyph { height: 84px; display: grid; place-items: center; }
.evo-stage .glyph svg { width: 72px; height: 72px; }
.evo-stage .glyph .glyph-text { font-family: var(--serif-zh); font-size: 3.2rem; line-height: 1; }
.evo-stage h4 { font-family: var(--serif-zh); font-size: 1rem; margin-top: .4rem; }
.evo-stage p { font-size: .74rem; color: var(--ink-soft); line-height: 1.35; }
.evo-arrow { align-self: center; color: var(--vermilion); font-size: 1.3rem; padding: 0 .1rem; }

/* liushu */
.liushu-grid {
  display: grid; gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
}
.liushu-card {
  background: var(--card-front); border-radius: var(--radius);
  padding: 1.2rem 1.3rem; box-shadow: var(--shadow);
  border-top: 4px solid var(--vermilion);
}
.liushu-card:nth-child(2) { border-top-color: var(--gold); }
.liushu-card:nth-child(3) { border-top-color: #4a6e5a; }
.liushu-card:nth-child(4) { border-top-color: #41597a; }
.liushu-card h3 { font-family: var(--serif-zh); font-size: 1.3rem; margin-bottom: .4rem; }
.liushu-card h3 span { font-family: var(--serif-en); font-size: .85rem; color: var(--ink-soft); font-weight: 400; margin-left: .4rem; }
.liushu-card p { font-size: .88rem; margin-bottom: .35rem; }
.liushu-card .zh { font-size: .82rem; color: var(--ink-soft); }

/* ---------- cards section ---------- */
.cards-section { padding: clamp(2.5rem, 6vw, 4.5rem) clamp(1.2rem, 5vw, 4rem); }
.cards-hint { color: var(--ink-soft); font-size: .92rem; margin-bottom: 1.4rem; }

.toolbar { display: flex; flex-wrap: wrap; gap: .8rem; align-items: center; margin-bottom: 1.8rem; }
#search {
  flex: 1 1 280px; max-width: 420px;
  font: inherit; font-size: .95rem;
  padding: .6rem 1rem; border-radius: 999px;
  border: 1.5px solid rgba(38,34,28,.25); background: var(--card-front); color: var(--ink);
  outline: none; transition: border-color .2s, box-shadow .2s;
}
#search:focus { border-color: var(--vermilion); box-shadow: 0 0 0 3px rgba(176,58,46,.15); }
.filters { display: flex; flex-wrap: wrap; gap: .45rem; }
.filter-btn {
  font: inherit; font-size: .82rem; cursor: pointer;
  padding: .38rem .9rem; border-radius: 999px;
  border: 1.5px solid rgba(38,34,28,.22); background: transparent; color: var(--ink-soft);
  transition: all .18s;
}
.filter-btn:hover { border-color: var(--vermilion); color: var(--vermilion); }
.filter-btn.active { background: var(--vermilion); border-color: var(--vermilion); color: #fdf6ec; }

/* card grid + flip cards */
.card-grid {
  display: grid; gap: 1.2rem;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
}
.card { perspective: 1400px; height: 330px; cursor: pointer; }
.card-inner {
  position: relative; width: 100%; height: 100%;
  transform-style: preserve-3d; transition: transform .65s cubic-bezier(.4,.1,.2,1);
}
.card.flipped .card-inner { transform: rotateY(180deg); }
.card-face {
  position: absolute; inset: 0; backface-visibility: hidden; -webkit-backface-visibility: hidden;
  border-radius: var(--radius); box-shadow: var(--shadow);
  display: flex; flex-direction: column; overflow: hidden;
}
.card:hover .card-inner { transform: translateY(-4px); }
.card.flipped:hover .card-inner { transform: rotateY(180deg) translateY(-4px); }

/* front */
.card-front { background: var(--card-front); padding: 1.1rem 1.1rem .9rem; }
.card-front .freq {
  position: absolute; top: .7rem; right: .85rem;
  font-size: .7rem; color: var(--ink-soft); letter-spacing: .05em;
}
.pict-row { display: flex; align-items: center; justify-content: center; gap: .55rem; margin-top: .5rem; }
.pict-row svg { width: 92px; height: 92px; }
.pict-row .to-modern { color: var(--vermilion); font-size: 1.25rem; }
.pict-row .modern-char {
  font-family: var(--serif-zh); font-weight: 600; font-size: 4.6rem; line-height: 1;
}
.card-front .pinyin {
  text-align: center; font-size: 1.35rem; color: var(--vermilion);
  font-weight: 600; margin-top: .7rem; font-family: var(--serif-py);
}
.card-front .meaning-en { text-align: center; font-size: 1.02rem; font-weight: 600; margin-top: .35rem; }
.card-front .meaning-zh { text-align: center; font-family: var(--serif-zh); font-size: .88rem; color: var(--ink-soft); margin-top: .15rem; }
.card-front .flip-hint {
  margin-top: auto; text-align: center; font-size: .72rem; color: rgba(91,83,69,.65); letter-spacing: .08em;
}

/* back */
.card-back {
  transform: rotateY(180deg);
  background: var(--card-back); color: #efe7d7;
  padding: 1.15rem 1.2rem 1rem;
}
.card-back .back-head { display: flex; align-items: baseline; gap: .6rem; margin-bottom: .55rem; }
.card-back .back-char { font-family: var(--serif-zh); font-size: 2rem; font-weight: 600; color: #f6f1e7; }
.card-back .back-py { color: #d9a05b; font-size: 1rem; font-family: var(--serif-py); }
.type-tag {
  display: inline-block; font-size: .68rem; letter-spacing: .06em;
  background: rgba(217,160,91,.18); color: #d9a05b;
  border: 1px solid rgba(217,160,91,.5);
  padding: .14rem .55rem; border-radius: 999px; margin-left: auto;
}
.card-back .story { font-size: .85rem; line-height: 1.5; color: #e6ddca; }
.card-back .story-zh { font-family: var(--serif-zh); font-size: .8rem; color: #b9ae97; margin-top: .45rem; line-height: 1.55; }
.card-back .example {
  margin-top: auto; padding-top: .6rem; border-top: 1px dashed rgba(239,231,215,.25);
  font-size: .82rem;
}
.card-back .example .w { font-family: var(--serif-zh); font-size: 1rem; color: #f6f1e7; font-weight: 600; }
.card-back .example .wp { color: #d9a05b; margin: 0 .35rem; font-family: var(--serif-py); }

.no-results { color: var(--ink-soft); font-size: .95rem; padding: 2rem 0; }

/* pictograph stroke style */
.pict-stroke { stroke: var(--ink); stroke-width: 5; stroke-linecap: round; stroke-linejoin: round; fill: none; }
.card-back .pict-stroke { stroke: #efe7d7; }
.pict-fill { fill: var(--ink); stroke: none; }

/* ---------- footer ---------- */
.site-footer {
  padding: 2.2rem clamp(1.2rem, 5vw, 4rem); border-top: 1px solid rgba(38,34,28,.12);
  font-size: .8rem; color: var(--ink-soft);
}
.site-footer .zh { margin-top: .25rem; font-size: .78rem; }

@media (max-width: 640px) {
  .site-header { flex-direction: column; gap: .8rem; }
  .evo-arrow { display: none; }
  .card { height: 400px; }
}

@media (prefers-reduced-motion: reduce) {
  .card-inner { transition: none; }
}