/* ------------------------------------------------------------------
   Sergey Prokudin — personal page
   Edit colours, spacing, and type sizes via the CSS variables below.
------------------------------------------------------------------ */

:root {
  /* Palette — neutral cool greys on near-black text. */
  --bg: #f6f7f8;
  --text: #171717;
  --muted: #6b6e72;
  --faint: #dcdee0;
  --link: #171717;
  --link-hover: #3d4651;

  /* Layout */
  --max-width: 840px;

  /* Typography */
  --body-size: 17px;
  --line: 1.68;

  /* Spacing scale */
  --space-xs: 0.45rem;
  --space-sm: 0.8rem;
  --space-md: 1.4rem;
  --space-lg: 2.4rem;
  --space-xl: 4.2rem;

  /* Portrait sizing — referenced by .portrait and by header padding. */
  --portrait-size: 192px;
  --portrait-gap: 1.75rem;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  /* Helvetica Neue (regular) as the body face. */
  font-family: "Helvetica Neue", "HelveticaNeue", Helvetica,
    "Arial Nova", Arial, sans-serif;
  font-weight: 400;
  font-size: var(--body-size);
  line-height: var(--line);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* Links: understated underline; warmer accent on hover. */
a {
  color: var(--link);
  text-decoration: none;
  border-bottom: 1px solid rgba(23, 23, 23, 0.28);
  transition: color 160ms ease, border-color 160ms ease;
}

a:hover,
a:focus {
  color: var(--link-hover);
  border-color: rgba(61, 70, 81, 0.5);
}

a:focus-visible {
  outline: 2px solid rgba(61, 70, 81, 0.5);
  outline-offset: 3px;
  border-radius: 1px;
}

/* ------------------------------------------------------------------
   Page shell
------------------------------------------------------------------ */

.page {
  width: min(var(--max-width), calc(100% - 40px));
  margin: 0 auto;
  padding: 72px 0 48px;
}

/* ------------------------------------------------------------------
   Header
------------------------------------------------------------------ */

header {
  position: relative;
  padding-bottom: var(--space-xl);
  /* Reserve space on the right so h1 and nav don't run under the portrait. */
  padding-right: calc(var(--portrait-size) + var(--portrait-gap));
}

/* Portrait in the top-right of the header.
   Square crop with slight corner rounding; resize via --portrait-size in :root. */
.portrait {
  position: absolute;
  top: 4px;
  right: 0;
  width: var(--portrait-size);
  height: var(--portrait-size);
  border-radius: 50%;
  object-fit: cover;
  display: block;
  /* Monochrome to keep the page palette unified. */
  filter: grayscale(1) contrast(1.02);
}

h1, h2, h3, p { margin: 0; }

h1 {
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(2.1rem, 5.6vw, 4.2rem);
  font-weight: 400;
  line-height: 1.0;
  letter-spacing: -0.045em;
  max-width: 760px;
}

.role {
  margin-top: var(--space-md);
  color: var(--muted);
  font-size: 1rem;
  line-height: 1.55;
}

.topics { color: var(--text); }

nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem 1rem;
  margin-top: var(--space-md);
  font-size: 0.95rem;
}

.hero {
  margin-top: var(--space-xl);
  max-width: 780px;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(1.2rem, 2.4vw, 1.75rem);
  line-height: 1.36;
  letter-spacing: -0.02em;
}

/* ------------------------------------------------------------------
   Sections
   Two columns on desktop: label on the left, content on the right.
   Collapses to a single column on mobile.
------------------------------------------------------------------ */

main { border-top: 1px solid var(--faint); }

section {
  display: grid;
  grid-template-columns: 180px 1fr;
  gap: var(--space-lg);
  padding: var(--space-xl) 0;
  border-bottom: 1px solid var(--faint);
}

h2 {
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  line-height: 1.4;
}

.section-body > p + p { margin-top: var(--space-md); }

/* ------------------------------------------------------------------
   Research grid (4 themes)
------------------------------------------------------------------ */

.research-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-lg);
}

.research-item h3 {
  font-size: 1.02rem;
  font-weight: 600;
  line-height: 1.35;
  margin-bottom: var(--space-xs);
}

.research-item p {
  color: var(--muted);
  font-size: 0.98rem;
  line-height: 1.58;
}

/* Inline list of selected works under each research theme. */
.work-refs {
  margin-top: var(--space-sm);
  font-size: 0.9rem;
  line-height: 1.5;
  color: var(--muted);
}

.work-refs a {
  border-bottom-color: rgba(23, 23, 23, 0.2);
}

/* "Full publication list" pointer below the research grid. */
.full-list {
  grid-column: 2;
  margin-top: var(--space-lg);
  font-size: 0.92rem;
  color: var(--muted);
}

/* ------------------------------------------------------------------
   Footer
------------------------------------------------------------------ */

footer {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--space-md);
  padding-top: var(--space-lg);
  color: var(--muted);
  font-size: 0.92rem;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem 1rem;
}

/* ------------------------------------------------------------------
   Responsive
------------------------------------------------------------------ */

@media (max-width: 760px) {
  :root {
    --body-size: 16px;
    --space-xl: 3.2rem;
    --portrait-size: 104px;
    --portrait-gap: 1.1rem;
  }

  .page {
    width: min(100% - 28px, var(--max-width));
    padding-top: 48px;
  }

  .portrait { top: 0; }

  section {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }

  .research-grid { grid-template-columns: 1fr; }

  .full-list { grid-column: 1; }
}

/* Respect users who prefer reduced motion. */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  a { transition: none; }
}