/* ========================================
   sections.css — #about / #now / #uses / #colophon
   只引用 style.css 中的语义变量，四套主题自动适配
   ======================================== */

/* =====================================================
   ABOUT
   ===================================================== */
.about-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(0, 0.6fr);
  gap: clamp(3rem, 7vw, 6.5rem);
  align-items: start;
}

.about-lead {
  font-family: var(--font-serif);
  font-size: clamp(1.5rem, 3vw, 2.25rem);
  font-weight: 600;
  line-height: 1.3;
  letter-spacing: -0.01em;
  color: var(--fg);
  text-wrap: balance;
  margin-bottom: 2rem;
}

.about-body {
  font-size: 1.0625rem;
  line-height: 1.75;
  color: var(--fg-muted);
  max-width: 62ch;
}
.about-body + .about-body { margin-top: 1.25rem; }

/* --- 侧栏事实列表 --- */
.about-side {
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
  padding-top: 0.5rem;
}

.about-facts {
  border-top: 1px solid var(--border);
}

.about-fact {
  display: grid;
  grid-template-columns: 9ch minmax(0, 1fr);
  gap: 1.25rem;
  align-items: baseline;
  padding: 0.9375rem 0;
  border-bottom: 1px solid var(--border);
}

.about-fact dt {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--fg-dim);
  transition: color 0.3s var(--ease);
}

.about-fact dd {
  font-size: 0.9375rem;
  font-weight: 400;
  color: var(--fg);
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.about-fact:hover dt { color: var(--accent); }

.about-fact.empty dd {
  display: inline-block;
  color: var(--fg-dim);
  border-bottom: 1px dashed var(--border-strong);
  padding-bottom: 0.125rem;
  min-width: 8ch;
}

/* --- 签名 --- */
.about-sig {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 0.875rem;
}

.about-sig .sig-line {
  display: block;
  width: 40px;
  height: 1px;
  background: var(--accent);
  flex: none;
}

.about-sig .sig-text {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  color: var(--fg-dim);
}

/* --- 原则三列 --- */
.principle-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: clamp(2rem, 4vw, 3.5rem);
  margin-top: clamp(4rem, 8vw, 6.5rem);
}

.principle-card {
  position: relative;
  padding-top: 1.5rem;
  background: none;
  border: 0;
}
.principle-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 1px;
  background: var(--border);
  transition: background-color 0.3s var(--ease);
}
.principle-card:hover::before { background: var(--accent); }

.principle-num {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.03em;
  color: var(--accent-dim);
  margin-bottom: 1.25rem;
  transition: color 0.3s var(--ease);
}
.principle-card:hover .principle-num { color: var(--accent); }

.principle-title {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.35;
  color: var(--fg);
  margin-bottom: 0.625rem;
}

.principle-desc {
  font-size: 0.9375rem;
  line-height: 1.7;
  color: var(--fg-muted);
}

/* =====================================================
   NOW
   ===================================================== */
.now-grid {
  border-top: 1px solid var(--border);
  max-width: 72ch;
}

.now-item {
  position: relative;
  display: grid;
  grid-template-columns: 8ch minmax(0, 1fr);
  gap: 1.5rem;
  align-items: baseline;
  padding: 1.25rem 0;
  border-bottom: 1px solid var(--border);
}

.now-item dt {
  position: relative;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
}
.now-item dt::before {
  content: '\2192';
  position: absolute;
  right: 100%;
  top: 0;
  margin-right: 0.5rem;
  color: var(--accent);
  opacity: 0;
  transform: translateX(-6px);
  transition: opacity 0.3s var(--ease), transform 0.3s var(--ease);
}
.now-item:hover dt::before {
  opacity: 1;
  transform: translateX(0);
}

.now-item dd {
  font-size: 1rem;
  line-height: 1.7;
  color: var(--fg);
}

/* =====================================================
   USES
   ===================================================== */
.uses-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 2rem;
}

.uses-group-title {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--fg-dim);
  padding-bottom: 0.75rem;
  margin-bottom: 0.75rem;
  border-bottom: 1px solid var(--border);
}

.uses-group ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.uses-group li {
  position: relative;
  font-size: 1rem;
  line-height: 1.9;
  color: var(--fg);
  padding-left: 1.125rem;
}
.uses-group li::before {
  content: '\00B7';
  position: absolute;
  left: 0;
  top: 0;
  color: var(--accent-dim);
  font-weight: 700;
  transition: color 0.25s var(--ease);
}
.uses-group li:hover::before { color: var(--accent); }

/* =====================================================
   COLOPHON（由 app.js 动态插入 footer 前）
   ===================================================== */
.colophon {
  max-width: 60ch;
  margin: 0 auto;
  text-align: center;
  position: relative;
}
.colophon::before {
  content: '';
  position: absolute;
  top: 0; left: clamp(1.25rem, 5vw, 4rem); right: clamp(1.25rem, 5vw, 4rem);
  height: 1px;
  background: var(--border);
}

.colophon-title {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--fg-dim);
  margin-bottom: 1.5rem;
}

.colophon-p {
  font-size: 0.9375rem;
  line-height: 1.75;
  color: var(--fg-muted);
  text-wrap: pretty;
}
.colophon-p + .colophon-p { margin-top: 0.875rem; }

.colophon-p2 {
  font-size: 0.875rem;
  color: var(--fg-dim);
}

/* =====================================================
   浅色主题微调：虚线/分割线在浅底上略提对比
   ===================================================== */
[data-palette="frost"] .about-fact.empty dd,
[data-palette="mist"] .about-fact.empty dd {
  border-bottom-color: rgba(var(--fg-rgb), 0.28);
}

/* =====================================================
   RESPONSIVE
   ===================================================== */
@media (max-width: 900px) {
  .about-grid {
    grid-template-columns: minmax(0, 1fr);
    gap: 3rem;
  }
  .about-side { padding-top: 0; }
  .principle-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 2.5rem 2rem;
  }
}

@media (max-width: 640px) {
  .about-lead { margin-bottom: 1.5rem; }
  .about-fact {
    grid-template-columns: minmax(0, 1fr);
    gap: 0.25rem;
    padding: 0.875rem 0;
  }
  .about-sig { justify-content: flex-start; }

  .principle-grid {
    grid-template-columns: minmax(0, 1fr);
    gap: 2rem;
  }

  .now-item {
    grid-template-columns: minmax(0, 1fr);
    gap: 0.375rem;
    padding: 1rem 0;
  }
  .now-item dt::before { display: none; }

  .uses-grid {
    grid-template-columns: minmax(0, 1fr);
    gap: 2.25rem;
  }
}

/* =====================================================
   REDUCED MOTION
   ===================================================== */
@media (prefers-reduced-motion: reduce) {
  .about-fact dt,
  .principle-card::before,
  .principle-num,
  .now-item dt::before,
  .uses-group li::before {
    transition: none;
  }
  .now-item dt::before {
    transform: none;
  }
}