/* =========================================================
   Charles Cheng Zhang — personal site
   Colours, fonts and spacing all live in the :root block
   below. Change a value there and it updates everywhere.
   ========================================================= */

:root {
  --ink:          #16181d;   /* main text            */
  --ink-soft:     #565c66;   /* secondary text       */
  --ink-faint:    #8b929d;   /* captions, meta       */
  --accent:       #002147;   /* Oxford blue — links  */
  --accent-soft:  #4a6f96;
  --rule:         #e4e6ea;   /* hairlines            */
  --surface:      #ffffff;   /* page background      */
  --surface-alt:  #f6f7f9;   /* sidebar background   */
  --pill-bg:      #ffffff;

  --serif: "EB Garamond", Georgia, "Times New Roman", serif;
  --sans:  "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;

  --sidebar-w: 310px;
  --gutter: 56px;
  --measure: 640px;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --ink:         #e6e8ec;
    --ink-soft:    #a7adb8;
    --ink-faint:   #7b828e;
    --accent:      #9fc3e8;
    --accent-soft: #7ba3cc;
    --rule:        #2a2e36;
    --surface:     #14161a;
    --surface-alt: #1a1d22;
    --pill-bg:     #1f2329;
  }
}
:root[data-theme="dark"] {
  --ink: #e6e8ec; --ink-soft: #a7adb8; --ink-faint: #7b828e;
  --accent: #9fc3e8; --accent-soft: #7ba3cc; --rule: #2a2e36;
  --surface: #14161a; --surface-alt: #1a1d22; --pill-bg: #1f2329;
}

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

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

body {
  margin: 0;
  background: var(--surface);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.62;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 2px; }

.skip-link {
  position: absolute; left: -9999px; top: 0;
  background: var(--accent); color: #fff; padding: 10px 16px; z-index: 10;
}
.skip-link:focus { left: 0; }

:focus-visible { outline: 2px solid var(--accent-soft); outline-offset: 3px; border-radius: 3px; }

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

.layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
  min-height: 100vh;
}

/* ---------------- sidebar ---------------- */

.sidebar {
  background: var(--surface-alt);
  border-right: 1px solid var(--rule);
}

.sidebar-inner {
  position: sticky;
  top: 0;
  padding: 52px 36px 48px;
  max-height: 100vh;
  overflow-y: auto;
}

.portrait-frame {
  position: relative;
  width: 100%;
  aspect-ratio: 1 / 1;
  border-radius: 50%;
  overflow: hidden;
  margin-bottom: 26px;
  background: var(--rule) radial-gradient(circle at 50% 38%, var(--ink-faint) 0 17%, transparent 17.5%);
}
/* soft shoulders for the fallback silhouette */
.portrait-frame::after {
  content: "";
  position: absolute;
  left: 50%; bottom: -22%;
  width: 78%; aspect-ratio: 1 / 1;
  transform: translateX(-50%);
  border-radius: 50%;
  background: var(--ink-faint);
}
.portrait {
  position: relative;
  z-index: 1;
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.portrait[hidden] { display: none; }
.name {
  font-family: var(--serif);
  font-size: 34px;
  line-height: 1.12;
  font-weight: 500;
  letter-spacing: -0.01em;
  margin: 0 0 8px;
}

.role {
  margin: 0 0 18px;
  color: var(--ink-soft);
  font-size: 14.5px;
  line-height: 1.5;
}

.cv-link { margin: 0 0 30px; font-size: 15px; }
.cv-link a { font-weight: 500; }

.sidebar .block { margin-bottom: 26px; }

.sidebar h2 {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 0 0 7px;
}

.sidebar .block p { margin: 0; font-size: 14.5px; }
.address { color: var(--ink-soft); line-height: 1.6; }

.media { list-style: none; margin: 0; padding: 0; font-size: 14.5px; }
.media li { margin-bottom: 3px; }

/* ---------------- content ---------------- */

.content {
  padding: 52px var(--gutter) 80px;
  max-width: calc(var(--measure) + var(--gutter) * 2);
}

.content section { margin-bottom: 52px; }

.section-title {
  font-family: var(--serif);
  font-size: 27px;
  font-weight: 600;
  letter-spacing: -0.005em;
  margin: 0 0 22px;
  padding-bottom: 9px;
  border-bottom: 1px solid var(--rule);
}

.bio { margin: 0; font-size: 16.5px; color: var(--ink); }
.bio + .bio { margin-top: 15px; }
.bio em { font-style: normal; font-weight: 600; }

/* ---------------- papers ---------------- */

.paper { margin-bottom: 30px; }
.paper:last-child { margin-bottom: 0; }

.paper-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 10px 18px;
}

.paper-title {
  font-family: var(--sans);
  font-size: 16px;
  font-weight: 600;
  line-height: 1.4;
  margin: 0;
  flex: 1 1 300px;
}

.paper-links {
  display: flex;
  gap: 7px;
  flex-wrap: wrap;
  flex: 0 0 auto;
}

.pill {
  font-family: var(--sans);
  font-size: 12px;
  font-weight: 500;
  line-height: 1;
  color: var(--ink-soft);
  background: var(--pill-bg);
  border: 1px solid var(--rule);
  border-radius: 5px;
  padding: 5px 9px;
  cursor: pointer;
  transition: border-color .15s ease, color .15s ease;
}
.pill:hover {
  color: var(--accent);
  border-color: var(--accent-soft);
  text-decoration: none;
}
.pill[aria-expanded="true"] {
  color: var(--accent);
  border-color: var(--accent-soft);
}

.coauthors, .status {
  margin: 5px 0 0;
  font-size: 14.5px;
  color: var(--ink-soft);
}
.status { color: var(--ink-faint); }

.abstract {
  margin-top: 12px;
  padding: 2px 0 2px 16px;
  border-left: 2px solid var(--rule);
}
.abstract p {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.62;
  color: var(--ink-soft);
  text-align: justify;
  hyphens: auto;
}
.abstract[hidden] { display: none; }

/* ---------------- lists & footer ---------------- */

.plain-list { list-style: none; margin: 0; padding: 0; }
.plain-list li { margin-bottom: 12px; }
.course { font-weight: 600; font-size: 16px; }
.meta { display: block; font-size: 14.5px; color: var(--ink-soft); }

.footer {
  margin-top: 64px;
  padding-top: 18px;
  border-top: 1px solid var(--rule);
  font-size: 13px;
  color: var(--ink-faint);
}
.footer p { margin: 0; }

/* ---------------- responsive ---------------- */

@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; }

  .sidebar { border-right: none; border-bottom: 1px solid var(--rule); }

  .sidebar-inner {
    position: static;
    max-height: none;
    overflow: visible;
    padding: 36px 16px 32px;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    column-gap: 20px;
  }

  .portrait-frame {
    flex: 0 0 116px;
    width: 116px;
    margin-bottom: 0;
  }

  .ident { flex: 1 1 200px; min-width: 0; }
  .name  { font-size: 26px; }
  .role  { margin-bottom: 10px; }
  .cv-link { margin-bottom: 0; }

  .sidebar .block {
    flex: 1 1 220px;
    margin: 26px 0 0;
  }

  .content { padding: 36px 16px 64px; max-width: none; }
  .section-title { font-size: 23px; }
  .abstract p { text-align: left; }
}

@media (max-width: 460px) {
  .sidebar-inner { display: block; }
  .portrait-frame { width: 104px; margin-bottom: 18px; }
  .paper-head { flex-direction: column; align-items: flex-start; gap: 8px; }
}

@media print {
  .sidebar { border: none; background: none; }
  .pill { display: none; }
  .abstract[hidden] { display: block !important; }
}