/* ==========================================================================
   Bipin Saha - Writeup / article template  ("archival" redesign, 2026)
   --------------------------------------------------------------------------
   Shared styling for every page under /writeups/. Builds on the tokens,
   reset, and fonts defined in /css/main.css - load that file FIRST, then
   this one. Same warm-ivory paper, one oxblood accent, hairlines not
   shadows, IBM Plex Mono for labels / dates / metrics.

   Contents
     1. Skip link
     2. Masthead-lite (wordmark + breadcrumb + language toggle)
     3. Article layout (contents rail + column)
     4. Article header (eyebrow, lede, meta, tags)
     5. Prose (headings, links, lists, quotes, rules)
     6. Figures & tables
     7. Code & equations
     8. Callouts & key-points
     9. References
    10. Prev / next nav
    11. Responsive
    12. Bilingual (English / Bangla) toggle
   ========================================================================== */


/* 1. Skip link ========================================================== */

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  background: var(--accent);
  color: #fff;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  padding: 0.5rem 0.9rem;
  border-radius: 0 0 6px 0;
}
.skip-link:focus { left: 0; }


/* 2. Masthead-lite ===================================================== */

.wm {
  border-bottom: 1px solid var(--line);
  background: var(--paper);
}
.wm-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.4rem 1.25rem;
  padding-top: 1.1rem;
  padding-bottom: 1.1rem;
}
.wm-home {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--head);
  letter-spacing: -0.01em;
}
.wm-home:hover { color: var(--accent-ink); text-decoration: none; }

.wm-crumbs {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.03em;
  color: var(--muted);
}
.wm-crumbs a { color: var(--accent-ink); }
.wm-crumbs span { margin: 0 0.35rem; color: var(--line); }
.wm-crumbs .here { color: var(--muted); margin-left: 0.35rem; }


/* 3. Article layout =================================================== */

.w-layout {
  display: grid;
  grid-template-columns: 10rem 1fr;
  gap: 3.5rem;
  padding: 3rem 0 3.5rem;
}

.w-toc { position: sticky; top: 2rem; align-self: start; }
.w-toc-label {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.75rem;
}
.w-toc ul { list-style: none; margin: 0; padding: 0; }
.w-toc a {
  display: block;
  padding: 0.3rem 0.6rem;
  border-left: 2px solid var(--line);
  font-family: var(--font-mono);
  font-size: 0.74rem;
  line-height: 1.4;
  color: var(--muted);
  transition: color 0.15s ease, border-color 0.15s ease, background-color 0.15s ease;
}
.w-toc a:hover { color: var(--ink); text-decoration: none; }
.w-toc a.is-active {
  color: var(--accent-ink);
  border-left-color: var(--accent);
  background: var(--accent-wash);
  font-weight: 500;
}

.warticle { min-width: 0; max-width: 44rem; }


/* 4. Article header ================================================== */

.w-eyebrow {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.7rem;
}
.w-eyebrow::before {
  content: "";
  display: inline-block;
  width: 0.9rem;
  height: 2px;
  background: var(--accent);
  vertical-align: 0.22em;
  margin-right: 0.5rem;
}

.warticle > h1 {
  font-size: clamp(1.9rem, 5vw, 2.6rem);
  line-height: 1.1;
  letter-spacing: -0.022em;
  margin: 0;
}

.w-lede {
  font-size: 1.15rem;
  line-height: 1.6;
  color: var(--ink);
  margin: 1.1rem 0 0;
}

.w-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem 1.2rem;
  margin: 1.3rem 0 0;
  padding: 0.7rem 0 0;
  border-top: 1px solid var(--line-soft);
  font-family: var(--font-mono);
  font-size: 0.73rem;
  color: var(--muted);
}

.w-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin: 0.9rem 0 0;
  padding: 0;
  list-style: none;
}
.w-tags li {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.03em;
  color: var(--muted);
  border: 1px solid var(--line);
  border-radius: 100px;
  padding: 0.18rem 0.62rem;
}


/* 5. Prose ========================================================== */

.prose { margin-top: 2.5rem; }
.prose > section + section { margin-top: 2.75rem; }

.prose h2 {
  font-size: 1.4rem;
  letter-spacing: -0.015em;
  border-bottom: 1px solid var(--line);
  padding-bottom: 0.4rem;
  margin: 0 0 1.1rem;
}
.prose h2 .s-num {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--accent-ink);
  margin-right: 0.6rem;
}
.prose h3 {
  font-size: 1.08rem;
  margin: 1.9rem 0 0.6rem;
  color: var(--head);
}

.prose p { margin: 0 0 1rem; }
.prose ul, .prose ol { margin: 0 0 1rem; padding-left: 1.3rem; }
.prose li { margin: 0.35rem 0; }
.prose li > ul, .prose li > ol { margin: 0.35rem 0 0.5rem; }

.prose strong { font-weight: 600; color: var(--head); }
.prose em { font-style: italic; }

.prose a { color: var(--accent-ink); text-decoration: none; border-bottom: 1px solid var(--line); }
.prose a:hover { border-bottom-color: var(--accent); text-decoration: none; }

/* heading anchor, injected by writeup.js */
.w-anchor {
  margin-left: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--line);
  border: 0 !important;
  opacity: 0;
  transition: opacity 0.15s ease, color 0.15s ease;
}
.prose h2:hover .w-anchor,
.prose h3:hover .w-anchor,
.w-anchor:focus { opacity: 1; color: var(--accent-ink); }

.prose blockquote {
  margin: 1.3rem 0;
  padding: 0.3rem 0 0.3rem 1.1rem;
  border-left: 2px solid var(--accent);
  color: var(--muted);
  font-style: italic;
}
.prose blockquote p:last-child { margin-bottom: 0; }

.prose hr {
  border: 0;
  border-top: 1px solid var(--line);
  margin: 2.5rem 0;
}

.ref-link {
  border: 0 !important;
  font-family: var(--font-mono);
  font-size: 0.72em;
  vertical-align: 0.35em;
  padding: 0 0.05em;
}


/* 6. Figures & tables =============================================== */

.prose figure { margin: 1.75rem 0; }
.prose figure img {
  display: block;
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 6px;
}
.prose figcaption {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  line-height: 1.5;
  color: var(--muted);
  margin-top: 0.6rem;
}

.t-wrap { overflow-x: auto; margin: 1.6rem 0; }
.prose table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
  min-width: 32rem;
}
.prose caption {
  caption-side: bottom;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--muted);
  text-align: left;
  padding-top: 0.6rem;
}
.prose th, .prose td {
  text-align: left;
  padding: 0.5rem 0.8rem;
  border-bottom: 1px solid var(--line-soft);
  vertical-align: top;
}
.prose thead th {
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
  border-bottom: 1px solid var(--line);
}
.prose tbody tr:last-child td { border-bottom: 1px solid var(--line); }
.prose td.num { font-family: var(--font-mono); white-space: nowrap; }


/* 7. Code & equations ============================================= */

.prose code {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: var(--paper-sink);
  border: 1px solid var(--line-soft);
  border-radius: 4px;
  padding: 0.08em 0.35em;
}
.prose pre {
  margin: 1.5rem 0;
  padding: 1rem 1.1rem;
  background: var(--paper-sink);
  border: 1px solid var(--line);
  border-radius: 6px;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.6;
}
.prose pre code {
  background: none;
  border: 0;
  padding: 0;
  font-size: inherit;
}

/* lightweight inline / display math - no external library */
.eq {
  font-family: var(--font-body);
  font-style: italic;
}
.eq sub, .eq sup { font-style: normal; font-size: 0.7em; }
.eq-block {
  margin: 1.4rem 0;
  padding: 0.9rem 1rem;
  background: var(--paper-sink);
  border-left: 2px solid var(--line);
  border-radius: 0 6px 6px 0;
  font-family: var(--font-body);
  font-style: italic;
  font-size: 1rem;
  line-height: 1.7;
  overflow-x: auto;
}
.eq-block .eq-num {
  float: right;
  font-family: var(--font-mono);
  font-style: normal;
  font-size: 0.78rem;
  color: var(--muted);
}


/* 8. Callouts & key-points ======================================= */

.w-note {
  margin: 1.6rem 0;
  padding: 0.9rem 1.1rem;
  background: var(--accent-wash);
  border-left: 2px solid var(--accent);
  border-radius: 0 6px 6px 0;
  font-size: 0.95rem;
}
.w-note p:last-child { margin-bottom: 0; }
.w-note b {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent-ink);
  display: block;
  margin-bottom: 0.35rem;
}

.w-key {
  margin: 2.25rem 0;
  padding: 1.25rem 1.4rem;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
}
.w-key h2 {
  border: 0;
  padding: 0;
  margin: 0 0 0.7rem;
  font-size: 0.74rem;
  font-family: var(--font-mono);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
}
.w-key ul { margin: 0; padding-left: 1.2rem; }
.w-key li { margin: 0.4rem 0; font-size: 0.95rem; }


/* 9. References ================================================== */

.w-refs { margin-top: 3rem; }
.w-refs h2 {
  font-size: 1.4rem;
  border-bottom: 1px solid var(--line);
  padding-bottom: 0.4rem;
  margin: 0 0 1.1rem;
}
.w-refs ol {
  margin: 0;
  padding-left: 1.6rem;
  font-size: 0.85rem;
  line-height: 1.6;
  color: var(--muted);
}
.w-refs li { margin: 0.5rem 0; }
.w-refs li::marker { font-family: var(--font-mono); font-size: 0.78rem; }
.w-refs a { color: var(--accent-ink); word-break: break-word; }


/* 10. Prev / next nav ========================================== */

.w-prevnext {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin-top: 3rem;
  padding-top: 1.75rem;
  border-top: 1px solid var(--line);
}
.w-prevnext a {
  display: block;
  padding: 0.9rem 1rem;
  border: 1px solid var(--line);
  border-radius: 6px;
  transition: border-color 0.18s ease;
}
.w-prevnext a:hover { border-color: var(--accent); text-decoration: none; }
.w-prevnext .dir {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.3rem;
}
.w-prevnext .ttl {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 0.9rem;
  color: var(--head);
  line-height: 1.3;
}
.w-prevnext .n { text-align: right; }
.w-prevnext .n.only { grid-column: 2; }


/* --- writeups index listing --- */
.w-index { padding: 2.75rem 0 3.5rem; max-width: 44rem; }
.w-index > h1 {
  font-size: clamp(1.9rem, 5vw, 2.5rem);
  letter-spacing: -0.02em;
  margin: 0;
}
.w-index > .lead {
  font-size: 1.1rem;
  color: var(--muted);
  margin: 1rem 0 0;
}
.w-list { list-style: none; padding: 0; margin: 2.25rem 0 0; }
.w-list > li {
  padding: 1.4rem 0;
  border-bottom: 1px solid var(--line-soft);
}
.w-list > li:last-child { border-bottom: 0; }
.w-list h2 {
  font-size: 1.1rem;
  line-height: 1.3;
  margin: 0;
}
.w-list h2 a { color: var(--head); }
.w-list h2 a:hover { color: var(--accent-ink); text-decoration: none; }
.w-list .w-list-meta {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--muted);
  margin: 0.4rem 0 0;
}
.w-list .w-list-sum {
  font-size: 0.95rem;
  color: var(--ink);
  margin: 0.5rem 0 0;
}


/* 11. Responsive ============================================== */

@media (max-width: 900px) {
  .w-layout { grid-template-columns: 1fr; gap: 0; padding: 2.25rem 0 3rem; }
  .w-toc { display: none; }
  .warticle { max-width: none; }
}

@media (max-width: 620px) {
  .w-prevnext { grid-template-columns: 1fr; }
  .w-prevnext .n, .w-prevnext .n.only { text-align: left; grid-column: auto; }
  .warticle > h1 { font-size: 1.7rem; }
  .w-lede { font-size: 1.05rem; }
}

@media print {
  .wm, .w-toc, .w-prevnext, .skip-link, .site-footer { display: none !important; }
  .w-layout { display: block; padding: 0; }
  .warticle { max-width: none; }
  .prose a { border: 0; color: inherit; }
  [data-lang]:not([data-lang="en"]) { display: none !important; }
}


/* 12. Bilingual (English / Bangla) toggle ===================================
   Every translatable block appears twice - once with data-lang="en", once
   with data-lang="bn". js/writeup.js sets <html lang="en|bn"> from a stored
   preference (a small inline <head> script applies it before first paint to
   avoid a flash). Bangla is hidden until chosen. Reference lists and paper
   titles stay English in both modes - citations are language-neutral. */

.lang-toggle {
  display: inline-flex;
  align-items: stretch;
  border: 1px solid var(--line);
  border-radius: 100px;
  overflow: hidden;
}
.lang-toggle button {
  appearance: none;
  -webkit-appearance: none;
  margin: 0;
  border: 0;
  background: transparent;
  cursor: pointer;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.03em;
  line-height: 1;
  padding: 0.28rem 0.72rem;
  color: var(--muted);
  transition: background-color 0.15s ease, color 0.15s ease;
}
.lang-toggle button + button { border-left: 1px solid var(--line); }
.lang-toggle button:hover { color: var(--ink); }
.lang-toggle button[aria-pressed="true"] {
  background: var(--accent);
  color: #fff;
}

/* Visibility: Bangla blocks are hidden by default; swap when <html lang="bn">. */
[data-lang="bn"] { display: none; }
html[lang="bn"] [data-lang="bn"] { display: revert; }
html[lang="bn"] [data-lang="en"] { display: none; }

/* Bangla typography - Noto Bengali families, loaded per page. Only the token
   values change; every existing rule keeps working through var(--font-*). */
html[lang="bn"] {
  --font-display: "Noto Sans Bengali", "Space Grotesk", "Segoe UI", system-ui, sans-serif;
  --font-body: "Noto Serif Bengali", "Newsreader", Georgia, serif;
  --font-mono: "Noto Sans Bengali", "IBM Plex Mono", ui-monospace, monospace;
}
html[lang="bn"] .w-lede,
html[lang="bn"] .prose,
html[lang="bn"] .w-key li,
html[lang="bn"] .w-note { line-height: 1.75; }