/* ==========================================================================
   Shilpak Banerjee — personal site
   Plain CSS, no build step. Colours are defined once below; dark mode
   follows the visitor's system setting.
   ========================================================================== */

:root {
  --bg: #fbfaf7;
  --surface: #ffffff;
  --ink: #1c1d1f;
  --muted: #5c6066;
  --faint: #868a90;
  --rule: #e5e2db;
  --accent: #1d5c73;
  --accent-hover: #123f50;
  --accent-soft: #e7f0f3;
  --tag: #f1efe9;

  --serif: "Source Serif 4", "Source Serif Pro", Georgia, "Times New Roman", serif;
  --sans: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;

  --page: 54rem;
  --gutter: 1.25rem;
  --radius: 10px;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #131517;
    --surface: #1a1d20;
    --ink: #e8e6e1;
    --muted: #a6aab0;
    --faint: #7f838a;
    --rule: #2d3135;
    --accent: #7fc3d8;
    --accent-hover: #a8d9e8;
    --accent-soft: #1b2b31;
    --tag: #23272b;
  }
}

/* ---------- base ---------- */

*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.0625rem;
  line-height: 1.62;
  font-optical-sizing: auto;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a {
  color: var(--accent);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
  text-decoration-color: color-mix(in srgb, var(--accent) 35%, transparent);
  transition: color .15s, text-decoration-color .15s;
}
a:hover { color: var(--accent-hover); text-decoration-color: currentColor; }
a:focus-visible, summary:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 3px;
}

h1, h2, h3 {
  font-family: var(--serif);
  font-weight: 600;
  line-height: 1.2;
  letter-spacing: -0.01em;
  margin: 0;
  text-wrap: balance;
}

p { margin: 0 0 1em; }

.skip-link {
  position: absolute;
  left: -999px;
  top: 0.5rem;
  background: var(--surface);
  color: var(--accent);
  padding: 0.5rem 0.9rem;
  border-radius: 6px;
  font-family: var(--sans);
  font-size: 0.9rem;
  z-index: 10;
}
.skip-link:focus { left: 0.75rem; }

.wrap {
  max-width: var(--page);
  margin: 0 auto;
  padding: 0 var(--gutter);
}

/* ---------- header & navigation ---------- */

.site-header {
  border-bottom: 1px solid var(--rule);
}
.site-header .wrap {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.75rem 2rem;
  flex-wrap: wrap;
  padding-top: 1.4rem;
  padding-bottom: 1.1rem;
}
.brand {
  font-family: var(--serif);
  font-size: 1.3rem;
  font-weight: 600;
  color: var(--ink);
  text-decoration: none;
  letter-spacing: -0.01em;
}
.brand:hover { color: var(--accent); }

.site-nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.25rem 1.4rem;
}
.site-nav a {
  font-family: var(--sans);
  font-size: 0.875rem;
  font-weight: 500;
  letter-spacing: 0.02em;
  color: var(--muted);
  text-decoration: none;
  padding: 0.2rem 0;
  border-bottom: 2px solid transparent;
}
.site-nav a:hover { color: var(--ink); }
.site-nav a[aria-current="page"] {
  color: var(--ink);
  border-bottom-color: var(--accent);
}

/* ---------- page layout ---------- */

main { padding: 2.75rem 0 3.5rem; }

.page-title {
  font-size: clamp(1.9rem, 1.4rem + 2vw, 2.5rem);
  margin-bottom: 0.4rem;
}
.page-lede {
  color: var(--muted);
  font-size: 1.05rem;
  max-width: 40rem;
  margin-bottom: 2.25rem;
}

section + section { margin-top: 3rem; }

.section-title {
  font-size: 1.45rem;
  padding-bottom: 0.5rem;
  margin-bottom: 0.25rem;
  border-bottom: 1px solid var(--rule);
}
.subsection-title {
  font-family: var(--sans);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--faint);
  margin: 1.9rem 0 0.2rem;
}
.section-title + .subsection-title { margin-top: 1.25rem; }

/* jump links at the top of long pages */
.toc {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: -1rem 0 2.5rem;
  padding: 0;
  list-style: none;
}
.toc a {
  display: inline-block;
  font-family: var(--sans);
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--muted);
  text-decoration: none;
  padding: 0.3rem 0.75rem;
  border: 1px solid var(--rule);
  border-radius: 999px;
  background: var(--surface);
}
.toc a:hover { color: var(--accent); border-color: var(--accent); }

/* ---------- home ---------- */

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 19rem;
  gap: 3rem;
  align-items: start;
}
.hero h1 {
  font-size: clamp(2.2rem, 1.5rem + 3vw, 3rem);
  margin-bottom: 0.35rem;
}
.hero .role {
  font-family: var(--sans);
  font-size: 0.95rem;
  color: var(--muted);
  margin-bottom: 1.6rem;
  line-height: 1.5;
}
.hero .role span { white-space: nowrap; }

.photo {
  width: 100%;
  aspect-ratio: 4 / 5;
  object-fit: cover;
  border-radius: var(--radius);
  margin-bottom: 1.25rem;
  display: block;
}

.card {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 1.25rem 1.3rem;
}
.card h2 {
  font-family: var(--sans);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--faint);
  margin-bottom: 0.65rem;
}
.card + .card { margin-top: 1rem; }
.card address {
  font-style: normal;
  font-size: 0.92rem;
  line-height: 1.55;
  color: var(--muted);
}
.contact-list {
  list-style: none;
  margin: 0 0 0.9rem;
  padding: 0;
  font-size: 0.95rem;
}
.contact-list li { margin-bottom: 0.3rem; overflow-wrap: anywhere; }
.contact-list .label {
  font-family: var(--sans);
  font-size: 0.78rem;
  color: var(--faint);
  display: inline-block;
  min-width: 3.4rem;
}

.profile-links {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}
.profile-links a {
  display: inline-block;
  font-family: var(--sans);
  font-size: 0.8rem;
  font-weight: 500;
  text-decoration: none;
  padding: 0.28rem 0.65rem;
  border-radius: 6px;
  background: var(--accent-soft);
  color: var(--accent);
}
.profile-links a:hover { background: var(--accent); color: var(--bg); }

.interests {
  list-style: none;
  padding: 0;
  margin: 0.4rem 0 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
}
.interests li {
  font-family: var(--sans);
  font-size: 0.85rem;
  padding: 0.3rem 0.75rem;
  border-radius: 999px;
  background: var(--tag);
  color: var(--ink);
}

.home-sections { margin-top: 3.25rem; }

.quick-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(12rem, 1fr));
  gap: 1rem;
  margin-top: 1.25rem;
}
.quick-links a {
  display: block;
  padding: 1rem 1.1rem;
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  background: var(--surface);
  text-decoration: none;
  color: var(--ink);
  transition: border-color .15s, transform .15s;
}
.quick-links a:hover { border-color: var(--accent); transform: translateY(-1px); }
.quick-links strong {
  display: block;
  font-weight: 600;
  margin-bottom: 0.15rem;
}
.quick-links span {
  font-family: var(--sans);
  font-size: 0.84rem;
  color: var(--muted);
  line-height: 1.45;
  display: block;
}

/* ---------- publication list ---------- */

.pubs, .entries {
  list-style: none;
  margin: 0;
  padding: 0;
}
.pub {
  display: grid;
  grid-template-columns: 3.6rem minmax(0, 1fr);
  gap: 0 1rem;
  padding: 1rem 0;
  border-bottom: 1px solid var(--rule);
}
.pub:last-child { border-bottom: 0; }
.pub-year {
  font-family: var(--sans);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--faint);
  padding-top: 0.2rem;
  font-variant-numeric: tabular-nums;
}
.pub-title {
  font-weight: 600;
  line-height: 1.38;
  margin-bottom: 0.15rem;
}
.pub-authors, .pub-venue {
  font-size: 0.96rem;
  color: var(--muted);
  line-height: 1.5;
}
.pub-authors strong { color: var(--ink); font-weight: 600; }
.pub-venue em { color: var(--ink); }

.links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.5rem;
}
.links a {
  font-family: var(--sans);
  font-size: 0.76rem;
  font-weight: 500;
  text-decoration: none;
  padding: 0.16rem 0.55rem;
  border: 1px solid var(--rule);
  border-radius: 5px;
  color: var(--accent);
  background: var(--surface);
}
.links a:hover { border-color: var(--accent); }

/* ---------- dated entries (talks, teaching, students) ---------- */

.year-group {
  display: grid;
  grid-template-columns: 3.6rem minmax(0, 1fr);
  gap: 0 1rem;
  padding: 0.9rem 0;
  border-bottom: 1px solid var(--rule);
}
.year-group:last-child { border-bottom: 0; }
.year-group > .year {
  margin: 0;
  font-family: var(--sans);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--faint);
  padding-top: 0.2rem;
  font-variant-numeric: tabular-nums;
}
.entry {
  display: grid;
  grid-template-columns: 5.6rem minmax(0, 1fr);
  gap: 0 0.9rem;
  padding: 0.2rem 0 0.45rem;
}
.entry-when {
  font-family: var(--sans);
  font-size: 0.82rem;
  color: var(--faint);
  padding-top: 0.18rem;
  font-variant-numeric: tabular-nums;
}
.entry-what { line-height: 1.5; }
.entry-what .where { color: var(--muted); }
.entry-what .code {
  font-family: var(--sans);
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--muted);
  margin-right: 0.35rem;
}

.tag {
  display: inline-block;
  font-family: var(--sans);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  padding: 0.08rem 0.42rem;
  border-radius: 4px;
  background: var(--tag);
  color: var(--muted);
  vertical-align: 0.12em;
  margin-left: 0.3rem;
  white-space: nowrap;
}

.institution {
  font-family: var(--serif);
  font-size: 1.08rem;
  font-weight: 600;
  margin: 1.9rem 0 0.35rem;
}
.institution small {
  display: block;
  font-family: var(--sans);
  font-size: 0.8rem;
  font-weight: 400;
  color: var(--faint);
  margin-top: 0.1rem;
}

details.institution-block { border-bottom: 1px solid var(--rule); }
details.institution-block > summary {
  cursor: pointer;
  list-style: none;
  padding: 1.1rem 0 0.9rem;
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 1rem;
}
details.institution-block > summary::-webkit-details-marker { display: none; }
details.institution-block > summary .institution { margin: 0; }
details.institution-block > summary::after {
  content: "+";
  font-family: var(--sans);
  font-size: 1.2rem;
  color: var(--faint);
  line-height: 1;
}
details.institution-block[open] > summary::after { content: "\2212"; }
details.institution-block > .entries { padding-bottom: 1rem; }

.people {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}
.person {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 1rem 1.1rem;
}
.person h4 {
  margin: 0 0 0.2rem;
  font-family: var(--serif);
  font-size: 1.05rem;
  font-weight: 600;
}
.person p {
  margin: 0.15rem 0 0;
  font-size: 0.92rem;
  color: var(--muted);
  line-height: 1.5;
}
.person .meta {
  font-family: var(--sans);
  font-size: 0.8rem;
  color: var(--faint);
}

.muted { color: var(--muted); }

.simple-list {
  list-style: none;
  margin: 0.5rem 0 0;
  padding: 0;
}
.simple-list li {
  padding: 0.55rem 0;
  border-bottom: 1px solid var(--rule);
  display: grid;
  grid-template-columns: 9.5rem minmax(0, 1fr);
  gap: 0 1rem;
}
.simple-list li:last-child { border-bottom: 0; }
.simple-list .when {
  font-family: var(--sans);
  font-size: 0.84rem;
  color: var(--faint);
  padding-top: 0.15rem;
}

/* ---------- CV timeline ---------- */

.timeline {
  list-style: none;
  margin: 0.75rem 0 0;
  padding: 0;
}
.timeline li {
  display: grid;
  grid-template-columns: 9.5rem minmax(0, 1fr);
  gap: 0 1.25rem;
  padding: 0.9rem 0;
  border-bottom: 1px solid var(--rule);
}
.timeline li:last-child { border-bottom: 0; }
.timeline .when {
  font-family: var(--sans);
  font-size: 0.85rem;
  color: var(--faint);
  padding-top: 0.15rem;
  font-variant-numeric: tabular-nums;
}
.timeline .what strong { font-weight: 600; display: block; }
.timeline .what span { color: var(--muted); font-size: 0.97rem; }

/* ---------- callout ---------- */

.callout {
  border: 1px solid var(--rule);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
  background: var(--surface);
  padding: 1.25rem 1.4rem;
  margin-top: 1rem;
}
.callout h3 { font-size: 1.2rem; margin-bottom: 0.4rem; }
.callout p:last-child { margin-bottom: 0; }

.button {
  display: inline-block;
  font-family: var(--sans);
  font-size: 0.88rem;
  font-weight: 600;
  text-decoration: none;
  padding: 0.55rem 1rem;
  border-radius: 7px;
  background: var(--accent);
  color: var(--bg);
}
.button:hover { background: var(--accent-hover); color: var(--bg); }

/* ---------- footer ---------- */

.site-footer {
  border-top: 1px solid var(--rule);
  font-family: var(--sans);
  font-size: 0.8rem;
  color: var(--faint);
}
.site-footer .wrap {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.5rem 1.5rem;
  padding-top: 1.4rem;
  padding-bottom: 2rem;
}
.site-footer a { color: var(--muted); }

/* ---------- small screens ---------- */

@media (max-width: 760px) {
  body { font-size: 1rem; }
  main { padding-top: 2rem; }
  .hero { grid-template-columns: 1fr; gap: 2rem; }
  .site-header .wrap { padding-top: 1.1rem; padding-bottom: 0.9rem; }
  .site-nav ul { gap: 0.2rem 1.1rem; }
}

@media (max-width: 560px) {
  .pub, .year-group { grid-template-columns: 1fr; }
  .pub-year, .year-group > .year { padding-top: 0; margin-bottom: 0.2rem; }
  .entry { grid-template-columns: 3.8rem minmax(0, 1fr); gap: 0 0.6rem; }
  .simple-list li, .timeline li { grid-template-columns: 1fr; }
  .simple-list .when, .timeline .when { margin-bottom: 0.1rem; }
}

/* ---------- print (CV and publication list print cleanly) ---------- */

@media print {
  :root {
    --bg: #fff; --surface: #fff; --ink: #000; --muted: #333; --faint: #555;
    --rule: #ccc; --accent: #000; --accent-soft: #fff; --tag: #eee;
  }
  body { font-size: 10.5pt; }
  .site-nav, .skip-link, .toc, .site-footer { display: none; }
  main { padding: 1rem 0; }
  a { text-decoration: none; }
  .links { display: none; }
  .pub, .entry, .timeline li { break-inside: avoid; }
  details.institution-block > summary::after { content: ""; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}