/* Bobo Labs — article layer. Reuses tokens from ../styles.css; only adds prose. */

.article {
  padding-block: clamp(3rem, 2rem + 5vw, 6rem) var(--space-section);
}

.article-wrap {
  max-width: 44rem;
  margin-inline: auto;
  padding-inline: var(--wrap-pad);
}

.back-link {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-muted);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color var(--duration) var(--ease),
              border-color var(--duration) var(--ease);
}
.back-link:hover { color: var(--color-ink); border-bottom-color: var(--color-accent); }

.article-eyebrow {
  font-family: var(--font-mono);
  font-size: var(--text-eyebrow);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-top: 2.5rem;
  margin-bottom: 1.25rem;
}

.article-title {
  font-size: clamp(2rem, 1.2rem + 3.5vw, 3.5rem);
  line-height: 1.05;
  letter-spacing: -0.035em;
  font-weight: 800;
  max-width: 18ch;
}

.article-lede {
  margin-top: 1.5rem;
  color: var(--color-muted);
  font-size: clamp(1.0625rem, 1rem + 0.4vw, 1.25rem);
  max-width: 56ch;
}

.article-body { margin-top: clamp(2.5rem, 1.5rem + 3vw, 4rem); }

.article-body h2 {
  font-size: clamp(1.375rem, 1rem + 1.4vw, 1.875rem);
  letter-spacing: -0.025em;
  font-weight: 700;
  margin-top: 3rem;
  padding-top: 1.25rem;
  border-top: 2px solid var(--color-ink);
}
.article-body h2:first-child { margin-top: 0; }

.article-body h3 {
  font-size: 1.125rem;
  font-weight: 700;
  margin-top: 2rem;
}

.article-body p { margin-top: 1.1rem; }
.article-body ul, .article-body ol { margin-top: 1.1rem; padding-left: 1.4rem; }
.article-body li { margin-top: 0.5rem; }

.article-body code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: oklch(95% 0 0);
  padding: 0.1rem 0.35rem;
}

.article-body strong { font-weight: 700; }

.article-body table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 1.5rem;
  font-size: 0.9375rem;
}
.article-body th, .article-body td {
  text-align: left;
  padding: 0.65rem 0.85rem;
  border: 1px solid var(--color-line);
  vertical-align: top;
}
.article-body th {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-muted);
}

.takeaway {
  margin-top: 2rem;
  padding: 1.5rem 1.75rem;
  border-left: 3px solid var(--color-accent);
  background: oklch(96.5% 0 0);
}
.takeaway p { margin-top: 0.6rem; }
.takeaway p:first-child { margin-top: 0; }

.article-foot {
  margin-top: clamp(3rem, 2rem + 3vw, 5rem);
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-line);
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-muted);
}

/* ============================================================
   v2 ENHANCEMENT — Linear/Stripe modern technical blog layer
   100% 向後相容：舊文章不加 .article--enhanced 不會改變
   ============================================================ */

/* 1. Reading progress bar（頂部進度條）-------------------------- */
.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: transparent;
  z-index: 100;
  pointer-events: none;
}
.reading-progress::after {
  content: "";
  display: block;
  height: 100%;
  width: var(--progress, 0%);
  background: var(--color-accent);
  transition: width 80ms linear;
}

/* 2. Byline meta line（Amy · 日期 · reading time）---------------- */
.article-meta {
  margin-top: 1rem;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  letter-spacing: 0.04em;
  color: var(--color-muted);
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem 0.85rem;
  align-items: center;
}
.article-meta-author {
  color: var(--color-ink);
  font-weight: 600;
}
.article-meta-sep {
  opacity: 0.4;
}
.article-meta-time::before {
  content: "⏱  ";
  opacity: 0.6;
}

/* 3. 兩欄 layout（main + sticky TOC）---------------------------- */
.article--enhanced .article-wrap {
  max-width: 72rem;
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(1.5rem, 1rem + 3vw, 3.5rem);
}

@media (min-width: 1024px) {
  .article--enhanced .article-wrap {
    grid-template-columns: 14rem 1fr;
  }
  .article--enhanced .article-toc {
    grid-column: 1;
    grid-row: 2 / span 99;
  }
  .article--enhanced .back-link,
  .article--enhanced .article-eyebrow,
  .article--enhanced .article-title,
  .article--enhanced .article-meta,
  .article--enhanced .article-lede {
    grid-column: 2;
  }
  .article--enhanced .article-body,
  .article--enhanced .formula-interactive,
  .article--enhanced .formula-related {
    grid-column: 2;
    max-width: 44rem;
  }
}

/* 4. Sticky TOC（左側目錄）------------------------------------- */
.article-toc {
  display: none;
}
@media (min-width: 1024px) {
  .article-toc {
    display: block;
    position: sticky;
    top: 4.5rem;
    align-self: start;
    max-height: calc(100vh - 6rem);
    overflow-y: auto;
    padding-right: 0.5rem;
    font-size: 0.875rem;
    border-left: 1px solid var(--color-line);
    padding-left: 1rem;
  }
}
.article-toc-title {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-muted);
  margin-bottom: 0.75rem;
  font-weight: 600;
}
.article-toc-list {
  list-style: none;
  margin: 0;
  padding: 0;
}
.article-toc-list li {
  margin: 0.45rem 0;
  line-height: 1.4;
}
.article-toc-list a {
  color: var(--color-muted);
  text-decoration: none;
  display: inline-block;
  border-left: 2px solid transparent;
  padding-left: 0.6rem;
  margin-left: -0.6rem;
  transition: color var(--duration) var(--ease),
              border-color var(--duration) var(--ease);
}
.article-toc-list a:hover {
  color: var(--color-ink);
}
.article-toc-list a.is-active {
  color: var(--color-accent);
  border-left-color: var(--color-accent);
  font-weight: 600;
}

/* 5. Section anchor offset（避免 sticky bar 擋到跳轉目標）------- */
.article--enhanced .article-body h2,
.article--enhanced .article-body h3 {
  scroll-margin-top: 4.5rem;
}

/* 6. Formula-box hover lift（微妙感）--------------------------- */
.article--enhanced .formula-box {
  transition: box-shadow var(--duration) var(--ease),
              transform var(--duration) var(--ease);
}
.article--enhanced .formula-box:hover {
  box-shadow: 0 6px 24px -8px oklch(0% 0 0 / 0.08);
  transform: translateY(-1px);
}

/* 7. 多色 callout（除原本 warning 色外，新增 info / tip / key）-- */
.formula-callout--info {
  background: oklch(96% 0.03 230);
  border-left-color: oklch(60% 0.16 230);
}
.formula-callout--info .formula-callout-title {
  color: oklch(40% 0.18 230);
}
.formula-callout--tip {
  background: oklch(97% 0.04 150);
  border-left-color: oklch(58% 0.16 150);
}
.formula-callout--tip .formula-callout-title {
  color: oklch(35% 0.16 150);
}
.formula-callout--key {
  background: oklch(96% 0.04 290);
  border-left-color: oklch(55% 0.18 290);
}
.formula-callout--key .formula-callout-title {
  color: oklch(38% 0.20 290);
}

/* 8. inline anchor link 樣式（hover 時 # 符號出現）-------------- */
.article--enhanced .article-body h2,
.article--enhanced .article-body h3 {
  position: relative;
}
.article--enhanced .article-body h2 .anchor-link,
.article--enhanced .article-body h3 .anchor-link {
  position: absolute;
  left: -1.4rem;
  top: 50%;
  transform: translateY(-50%);
  opacity: 0;
  color: var(--color-muted);
  font-weight: 400;
  text-decoration: none;
  transition: opacity var(--duration) var(--ease);
}
.article--enhanced .article-body h2:hover .anchor-link,
.article--enhanced .article-body h3:hover .anchor-link {
  opacity: 0.6;
}
.article--enhanced .article-body h2 .anchor-link:hover,
.article--enhanced .article-body h3 .anchor-link:hover {
  opacity: 1;
  color: var(--color-accent);
}