/* ================================================================
   Sahithyan Sivakumaran — Academic Website
   A clean, serif-led minimal theme with dark/light mode
   ================================================================ */

/* --- CSS Variables: Light mode (default) --- */
:root {
  --bg: #f8f5ef;
  --bg-elev: #ffffff;
  --text: #2a2a28;
  --text-muted: #6b6b68;
  --text-soft: #9a9a96;
  --accent: #8b4513;
  --accent-soft: #c9a77a;
  --border: #e4ded0;
  --border-soft: #eee8dc;

  --font-serif: "Iowan Old Style", "Palatino Linotype", "URW Palladio L", Palatino, "Book Antiqua", Georgia, serif;
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "SF Mono", "Monaco", "Inconsolata", "Fira Mono", monospace;

  --max-width: 720px;
  --radius: 8px;
}

/* --- Dark mode (auto-detected via OS preference) --- */
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #1a1a1a;
    --bg-elev: #242424;
    --text: #e8e6e1;
    --text-muted: #a8a6a1;
    --text-soft: #6b6966;
    --accent: #d4a373;
    --accent-soft: #8b6a4a;
    --border: #3a3a38;
    --border-soft: #2d2d2c;
  }
}

/* --- Manual toggle override --- */
:root[data-theme="dark"] {
  --bg: #1a1a1a;
  --bg-elev: #242424;
  --text: #e8e6e1;
  --text-muted: #a8a6a1;
  --text-soft: #6b6966;
  --accent: #d4a373;
  --accent-soft: #8b6a4a;
  --border: #3a3a38;
  --border-soft: #2d2d2c;
}

:root[data-theme="light"] {
  --bg: #f8f5ef;
  --bg-elev: #ffffff;
  --text: #2a2a28;
  --text-muted: #6b6b68;
  --text-soft: #9a9a96;
  --accent: #8b4513;
  --accent-soft: #c9a77a;
  --border: #e4ded0;
  --border-soft: #eee8dc;
}

/* --- Reset & Base --- */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-serif);
  font-size: 17px;
  line-height: 1.7;
  min-height: 100vh;
  transition: background 0.3s ease, color 0.3s ease;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 32px 28px 80px;
}

/* --- Navigation --- */
.nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 0 36px;
  border-bottom: 1px solid var(--border-soft);
  margin-bottom: 40px;
  flex-wrap: wrap;
  gap: 12px;
}

.nav-brand {
  font-family: var(--font-sans);
  font-size: 15px;
  font-weight: 500;
  letter-spacing: -0.01em;
  color: var(--text);
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 24px;
  align-items: center;
}

.nav-links a {
  font-family: var(--font-sans);
  font-size: 14px;
  color: var(--text-muted);
  text-decoration: none;
  letter-spacing: 0.01em;
  transition: color 0.2s;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--accent);
}

/* --- Theme Toggle Button --- */
.theme-toggle {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-muted);
  width: 32px;
  height: 32px;
  border-radius: 50%;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  transition: all 0.2s;
  padding: 0;
}

.theme-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* --- Typography --- */
h1, h2, h3, h4 {
  font-family: var(--font-serif);
  font-weight: 500;
  color: var(--text);
  letter-spacing: -0.015em;
}

h1 {
  font-size: 34px;
  line-height: 1.15;
  margin-bottom: 8px;
}

h2 {
  font-size: 22px;
  margin-top: 48px;
  margin-bottom: 18px;
  font-weight: 500;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-soft);
}

h3 {
  font-size: 18px;
  margin-top: 24px;
  margin-bottom: 10px;
}

p {
  margin-bottom: 18px;
  color: var(--text);
}

a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s;
}

a:hover {
  border-bottom-color: var(--accent);
}

em {
  color: var(--text-muted);
}

strong {
  font-weight: 600;
  color: var(--text);
}

/* --- Hero / About section --- */
.hero {
  display: flex;
  gap: 28px;
  align-items: flex-start;
  margin-bottom: 36px;
}

.hero-photo {
  width: 130px;
  height: 130px;
  border-radius: 50%;
  object-fit: cover;
  flex-shrink: 0;
  border: 2px solid var(--border);
}

.hero-text {
  flex: 1;
  min-width: 0;
}

.hero-subtitle {
  font-family: var(--font-sans);
  font-size: 15px;
  color: var(--text-muted);
  margin-bottom: 14px;
  letter-spacing: 0.01em;
}

.hero-links {
  display: flex;
  gap: 14px;
  font-family: var(--font-sans);
  font-size: 13.5px;
  flex-wrap: wrap;
}

.hero-links a {
  color: var(--text-muted);
  border-bottom: 1px solid transparent;
}

.hero-links a:hover {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.hero-links span.sep {
  color: var(--text-soft);
}

/* --- Section styling --- */
.intro {
  font-size: 17.5px;
  line-height: 1.8;
  margin-bottom: 12px;
}

/* --- Lists --- */
ul, ol {
  margin-bottom: 20px;
  padding-left: 22px;
}

li {
  margin-bottom: 8px;
  color: var(--text);
}

/* --- News list --- */
.news-list {
  list-style: none;
  padding-left: 0;
}

.news-list li {
  padding: 12px 0;
  border-bottom: 1px dashed var(--border-soft);
  display: flex;
  gap: 18px;
  align-items: baseline;
  font-size: 15.5px;
}

.news-list li:last-child {
  border-bottom: none;
}

.news-date {
  font-family: var(--font-sans);
  font-size: 13px;
  color: var(--text-soft);
  flex-shrink: 0;
  width: 92px;
  letter-spacing: 0.02em;
}

/* --- Publication entries --- */
.pub {
  padding: 18px 0;
  border-bottom: 1px solid var(--border-soft);
}

.pub:last-child {
  border-bottom: none;
}

.pub-title {
  font-size: 17px;
  line-height: 1.4;
  margin-bottom: 6px;
  font-weight: 500;
  color: var(--text);
}

.pub-authors {
  font-size: 15px;
  color: var(--text-muted);
  margin-bottom: 4px;
}

.pub-authors .self {
  color: var(--text);
  font-weight: 500;
}

.pub-venue {
  font-family: var(--font-sans);
  font-size: 13.5px;
  color: var(--text-soft);
  font-style: italic;
  margin-bottom: 8px;
}

.pub-links {
  display: flex;
  gap: 12px;
  font-family: var(--font-sans);
  font-size: 12.5px;
  margin-top: 6px;
}

.pub-links a {
  color: var(--accent);
  padding: 2px 10px;
  border: 1px solid var(--accent-soft);
  border-radius: 14px;
  text-decoration: none;
  transition: all 0.2s;
}

.pub-links a:hover {
  background: var(--accent);
  color: var(--bg);
  border-color: var(--accent);
}

.pub-tag {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 11.5px;
  color: var(--text-soft);
  padding: 2px 8px;
  border: 1px solid var(--border);
  border-radius: 10px;
  margin-left: 6px;
  letter-spacing: 0.03em;
  text-transform: uppercase;
}

/* --- Writing list (index page) --- */
.writing-list {
  display: flex;
  flex-direction: column;
}

.writing-item {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 16px 0;
  border-bottom: 1px dashed var(--border-soft);
  text-decoration: none;
  gap: 18px;
  transition: color 0.2s;
}

.writing-item:last-child {
  border-bottom: none;
}

.writing-item:hover {
  border-bottom-color: var(--border-soft);
}

.writing-title {
  font-size: 17px;
  font-weight: 500;
  color: var(--text);
  line-height: 1.4;
  transition: color 0.2s;
}

.writing-item:hover .writing-title {
  color: var(--accent);
}

.writing-date {
  font-family: var(--font-sans);
  font-size: 13px;
  color: var(--text-soft);
  flex-shrink: 0;
  letter-spacing: 0.02em;
}

/* --- Writing article (individual post) --- */
.writing-back {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 13.5px;
  color: var(--text-muted);
  margin-bottom: 28px;
  text-decoration: none;
  border-bottom: none;
  transition: color 0.2s;
}

.writing-back:hover {
  color: var(--accent);
}

.writing-article h1 {
  margin-bottom: 6px;
}

.writing-meta {
  font-family: var(--font-sans);
  font-size: 13.5px;
  color: var(--text-soft);
  font-style: italic;
  margin-bottom: 32px;
}

.writing-article p {
  margin-bottom: 20px;
}

.writing-article code {
  font-family: var(--font-mono);
  font-size: 14px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  padding: 1px 5px;
  border-radius: 4px;
}

/* --- CV specific --- */
.cv-entry {
  display: flex;
  gap: 20px;
  padding: 12px 0;
  border-bottom: 1px dashed var(--border-soft);
  align-items: baseline;
}

.cv-entry:last-child {
  border-bottom: none;
}

.cv-date {
  font-family: var(--font-sans);
  font-size: 13px;
  color: var(--text-soft);
  flex-shrink: 0;
  width: 110px;
  letter-spacing: 0.02em;
}

.cv-content {
  flex: 1;
}

.cv-content .role {
  font-weight: 500;
  color: var(--text);
  font-size: 16px;
}

.cv-content .place {
  font-size: 14.5px;
  color: var(--text-muted);
}

.cv-content .advisor {
  font-size: 13.5px;
  color: var(--text-soft);
  font-family: var(--font-sans);
  font-style: italic;
  margin-top: 3px;
}

/* --- Download button --- */
.btn {
  display: inline-block;
  padding: 8px 16px;
  background: var(--accent);
  color: var(--bg);
  font-family: var(--font-sans);
  font-size: 13.5px;
  border-radius: 6px;
  border: none;
  text-decoration: none;
  transition: opacity 0.2s;
  letter-spacing: 0.01em;
}

.btn:hover {
  opacity: 0.85;
  border-bottom: none;
}

/* --- Footer --- */
.footer {
  margin-top: 80px;
  padding-top: 24px;
  border-top: 1px solid var(--border-soft);
  font-family: var(--font-sans);
  font-size: 12.5px;
  color: var(--text-soft);
  text-align: center;
}

/* --- Mobile responsive --- */
@media (max-width: 640px) {
  .container {
    padding: 20px 18px 60px;
  }

  .hero {
    flex-direction: column;
    align-items: center;
    text-align: center;
    gap: 18px;
  }

  .hero-photo {
    width: 110px;
    height: 110px;
  }

  .hero-links {
    justify-content: center;
  }

  h1 {
    font-size: 28px;
  }

  h2 {
    font-size: 20px;
  }

  body {
    font-size: 16px;
  }

  .nav {
    padding-bottom: 24px;
    margin-bottom: 28px;
  }

  .nav-links {
    gap: 16px;
  }

  .news-list li,
  .cv-entry,
  .writing-item {
    flex-direction: column;
    gap: 2px;
  }

  .news-date,
  .cv-date {
    width: auto;
  }
}