/* ── Nord palette ───────────────────────────────────────── */
:root {
  --nord0:  #2E3440;
  --nord1:  #3B4252;
  --nord2:  #434C5E;
  --nord3:  #4C566A;
  --nord4:  #D8DEE9;
  --nord5:  #E5E9F0;
  --nord6:  #ECEFF4;
  --nord7:  #8FBCBB;
  --nord8:  #88C0D0;
  --nord9:  #81A1C1;
  --nord10: #5E81AC;
  --nord11: #BF616A;
  --nord14: #A3BE8C;
  --nord15: #B48EAD;

  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 2rem;
  --space-lg: 4rem;
  --space-xl: 6rem;

  --max-width:  1000px;
  --nav-height: 60px;
  --radius:     6px;
}

/* ── Reset ──────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-height);
}

body {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 1rem;
  line-height: 1.7;
  color: var(--nord4);
  background-color: var(--nord0);
}

h1, h2, h3 { color: var(--nord6); font-weight: 600; line-height: 1.25; }

a { color: var(--nord8); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--nord6); }

/* ── Layout ─────────────────────────────────────────────── */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-md);
}

section { padding: var(--space-xl) 0; }

section[id] { scroll-margin-top: var(--nav-height); }

.section-heading {
  font-size: 1.5rem;
  margin-bottom: var(--space-md);
  padding-bottom: var(--space-xs);
  border-bottom: 1px solid var(--nord3);
  color: var(--nord6);
}

/* ── Focus (accessibility) ──────────────────────────────── */
:focus-visible {
  outline: 2px solid var(--nord8);
  outline-offset: 3px;
  border-radius: 2px;
}

/* ── Navigation ─────────────────────────────────────────── */
#nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  height: var(--nav-height);
  background: transparent;
  transition: background 0.3s ease, box-shadow 0.3s ease;
}

#nav.scrolled {
  background: var(--nord1);
  box-shadow: 0 1px 0 var(--nord2);
}

.nav-inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-name {
  font-weight: 600;
  font-size: 1rem;
  color: var(--nord6);
  letter-spacing: 0.01em;
}

.nav-name:hover { color: var(--nord8); }

#nav-links {
  display: flex;
  list-style: none;
  gap: var(--space-md);
}

#nav-links a {
  font-size: 0.9rem;
  color: var(--nord4);
  font-weight: 400;
}

#nav-links a:hover,
#nav-links a.active { color: var(--nord8); }

#hamburger {
  display: none;
  flex-direction: column;
  justify-content: space-between;
  width: 24px;
  height: 18px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0;
}

#hamburger span {
  display: block;
  height: 2px;
  background: var(--nord6);
  border-radius: 2px;
}

@media (max-width: 640px) {
  #hamburger { display: flex; }

  #nav-links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0; right: 0;
    flex-direction: column;
    background: var(--nord1);
    padding: var(--space-sm) var(--space-md);
    gap: var(--space-sm);
    border-bottom: 1px solid var(--nord2);
  }

  #nav-links.open { display: flex; }
}

/* ── Hero ───────────────────────────────────────────────── */
#hero {
  min-height: 100svh;
  display: flex;
  align-items: center;
  padding-top: var(--nav-height);
  background: linear-gradient(160deg, var(--nord0) 60%, var(--nord1) 100%);
}

.hero-inner {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--space-lg);
  align-items: center;
}

.hero-photo img {
  width: 220px;
  height: 220px;
  border-radius: 50%;
  object-fit: cover;
  object-position: center top;
  border: 3px solid var(--nord3);
  display: block;
}

.hero-text h1 {
  font-size: clamp(2rem, 5vw, 3rem);
  margin-bottom: var(--space-xs);
}

.hero-title {
  font-size: 1rem;
  color: var(--nord9);
  margin-bottom: var(--space-sm);
  font-weight: 400;
}

.hero-tagline {
  font-size: 1.125rem;
  color: var(--nord5);
  max-width: 52ch;
  margin-bottom: var(--space-md);
  line-height: 1.6;
}

.hero-ctas { display: flex; gap: var(--space-sm); flex-wrap: wrap; }

.btn {
  display: inline-block;
  padding: 0.6rem 1.4rem;
  border-radius: var(--radius);
  font-size: 0.9rem;
  font-weight: 500;
  transition: background 0.2s, color 0.2s, border-color 0.2s;
}

.btn-primary { background: var(--nord8); color: var(--nord0); }
.btn-primary:hover { background: var(--nord7); color: var(--nord0); }

.btn-secondary {
  background: transparent;
  color: var(--nord4);
  border: 1px solid var(--nord3);
}
.btn-secondary:hover { border-color: var(--nord8); color: var(--nord8); }

@media (max-width: 640px) {
  .hero-inner {
    grid-template-columns: 1fr;
    justify-items: center;
    text-align: center;
    gap: var(--space-md);
  }
  .hero-tagline { max-width: 100%; }
  .hero-ctas { justify-content: center; }
}

/* ── Research Themes ────────────────────────────────────── */
#research { background: var(--nord1); }

.research-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
}

.research-label {
  font-size: 0.775rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--nord8);
  margin-bottom: var(--space-sm);
}

.research-card p {
  color: var(--nord4);
  font-size: 1.05rem;
  line-height: 1.75;
}

@media (max-width: 640px) {
  .research-grid { grid-template-columns: 1fr; }
}

/* ── Technical Toolkit ──────────────────────────────────── */
#toolkit { background: var(--nord0); }

.toolkit-groups {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-md) var(--space-lg);
}

@media (max-width: 768px) {
  .toolkit-groups {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 480px) {
  .toolkit-groups {
    grid-template-columns: 1fr;
  }
}

.toolkit-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--nord9);
  margin-bottom: var(--space-xs);
}

.pill-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  list-style: none;
}

.pill {
  display: inline-block;
  padding: 0.2rem 0.7rem;
  border-radius: 999px;
  font-size: 0.825rem;
  color: var(--nord8);
  border: 1px solid var(--nord8);
  background: color-mix(in srgb, var(--nord8) 8%, transparent);
}

/* ── Publications ───────────────────────────────────────── */
#publications { background: var(--nord1); }

.publications-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-bottom: var(--space-md);
}

.publications-header .section-heading { margin-bottom: 0; }

.scholar-link {
  font-size: 0.875rem;
  color: var(--nord9);
  white-space: nowrap;
}

.scholar-link .ai { margin-left: 0.25rem; }

.publications-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.pub-title {
  color: var(--nord6);
  font-weight: 500;
  display: block;
}

.pub-title[href]:hover { color: var(--nord8); }

.pub-meta {
  font-size: 0.875rem;
  color: var(--nord3);
  margin-top: 0.15rem;
}

.pub-doi {
  font-size: 0.75rem;
  color: var(--nord4);
  border: 1px solid var(--nord3);
  border-radius: 3px;
  padding: 0 0.3em;
  margin-left: 0.4em;
  vertical-align: middle;
  text-decoration: none;
}

.pub-doi:hover {
  color: var(--nord8);
  border-color: var(--nord8);
}

.pub-loading {
  color: var(--nord3);
  font-style: italic;
}

/* ── Open Source / Software ─────────────────────────────── */
#software { background: var(--nord0); }

.software-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-md);
}

.software-card {
  background: var(--nord1);
  border-radius: var(--radius);
  padding: var(--space-md);
  border-top: 3px solid transparent;
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
}

.software-card--authored    { border-top-color: var(--nord14); }
.software-card--maintainer { border-top-color: var(--nord15); }
.software-card--contrib    { border-top-color: var(--nord8); }

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-xs);
}

.card-name {
  font-size: 1rem;
  font-weight: 600;
  color: var(--nord6);
}

.card-badge {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 0.1rem 0.5rem;
  border-radius: 999px;
  white-space: nowrap;
}

.card-badge--authored {
  background: color-mix(in srgb, var(--nord14) 20%, transparent);
  color: var(--nord14);
}

.card-badge--maintainer {
  background: color-mix(in srgb, var(--nord15) 20%, transparent);
  color: var(--nord15);
}

.card-badge--contrib {
  background: color-mix(in srgb, var(--nord8) 15%, transparent);
  color: var(--nord8);
}

.card-desc {
  font-size: 0.9rem;
  color: var(--nord4);
  flex: 1;
}

.card-links {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.card-link {
  font-size: 0.825rem;
  color: var(--nord9);
}

.card-link:hover { color: var(--nord8); }
.card-link .fab  { margin-right: 0.3rem; }

.card-link--secondary {
  color: var(--nord3);
  font-size: 0.775rem;
}

.card-link--secondary:hover { color: var(--nord9); }

@media (max-width: 768px) {
  .software-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 480px) {
  .software-grid { grid-template-columns: 1fr; }
}

/* ── About / Contact ────────────────────────────────────── */
#about { background: var(--nord1); }

.about-note {
  font-size: 1.05rem;
  color: var(--nord4);
  max-width: 55ch;
  margin-bottom: var(--space-md);
}

.contact-row {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
  align-items: center;
}

.contact-link {
  font-size: 1.75rem;
  color: var(--nord3);
  display: inline-flex;
  transition: color 0.2s, transform 0.2s;
}

.contact-link:hover {
  color: var(--nord8);
  transform: translateY(-2px);
}

/* ── Section background alternation ─────────────────────── */
/* hero:         nord0  (set on #hero)          */
/* research:     nord1  (set on #research)      */
/* toolkit:      nord0  (set on #toolkit)       */
/* publications: nord1  (set on #publications)  */
/* software:     nord0  (set on #software)      */
/* about:        nord1  (set on #about)         */

/* All section backgrounds are already set above.          */
/* This rule ensures the footer matches the final section. */

/* ── Footer ─────────────────────────────────────────────── */
footer {
  background: var(--nord1);
  padding: var(--space-md) 0;
  text-align: center;
  font-size: 0.875rem;
  color: var(--nord3);
  border-top: 1px solid var(--nord2);
}