/* ============================================================
   CESTC 2026 – Central European Symposium on Theoretical Chemistry
   Shared Stylesheet
   ============================================================ */

/* ── 1. Custom Properties ─────────────────────────────────── */
:root {
  /* Palette – Toruń medieval brick */
  --bg-dark:       #1a0f0a;
  --bg-mid:        #2e1a14;
  --bg-card:       #3a2318;
  --accent:        #c0432b;
  --accent-hover:  #e05a3a;
  --accent-dim:    rgba(192, 67, 43, 0.15);
  --accent-border: rgba(192, 67, 43, 0.30);
  --text:          #f2ede8;
  --text-muted:    #b0a49e;
  --text-on-accent:#ffffff;
  --border:        rgba(192, 67, 43, 0.25);
  --border-subtle: rgba(255, 255, 255, 0.08);

  /* Layout */
  --max-width:     1180px;
  --header-h:      72px;
  --radius:        10px;
  --radius-sm:     6px;

  /* Spacing */
  --sp-1: 0.5rem;
  --sp-2: 1rem;
  --sp-3: 1.5rem;
  --sp-4: 2rem;
  --sp-6: 3rem;
  --sp-8: 4rem;

  /* Typography */
  --font-body: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Mono', monospace;

  /* Transitions */
  --trans: 0.25s ease;
}

/* ── 2. Reset & Base ──────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg-mid);
  min-height: 100vh;
}

img, svg { display: block; max-width: 100%; }
a { color: var(--accent); text-decoration: none; transition: color var(--trans); }
a:hover { color: var(--accent-hover); }
ul { list-style: none; }

/* ── 3. Typography Scale ──────────────────────────────────── */
h1, h2, h3, h4, h5 {
  line-height: 1.2;
  font-weight: 700;
  color: var(--text);
}

h1 { font-size: clamp(2rem,   5vw + 0.5rem, 3.5rem); }
h2 { font-size: clamp(1.5rem, 3vw + 0.25rem, 2.25rem); }
h3 { font-size: clamp(1.1rem, 2vw + 0.1rem, 1.5rem); }
h4 { font-size: 1.1rem; }
p  { margin-bottom: var(--sp-2); }
p:last-child { margin-bottom: 0; }

/* Decorative section heading */
.section-title {
  position: relative;
  display: inline-block;
  margin-bottom: var(--sp-4);
  color: var(--text);
}
.section-title::after {
  content: '';
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 48px;
  height: 3px;
  background: var(--accent);
  border-radius: 2px;
}
.section-title.centered { display: block; text-align: center; }
.section-title.centered::after { left: 50%; transform: translateX(-50%); }

/* ── 4. Layout Utilities ──────────────────────────────────── */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--sp-3);
  width: 100%;
}

.section {
  padding: var(--sp-8) 0;
}
.section--dark  { background: var(--bg-dark); }
.section--mid   { background: var(--bg-mid); }
.section--card  { background: var(--bg-card); }

.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--sp-4); }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--sp-4); }
.grid-auto { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: var(--sp-3); }
.grid-auto-sm { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: var(--sp-3); }

.flex-center { display: flex; align-items: center; justify-content: center; }
.flex-between { display: flex; align-items: center; justify-content: space-between; }
.flex-col { display: flex; flex-direction: column; }
.gap-2 { gap: var(--sp-2); }
.gap-3 { gap: var(--sp-3); }

.text-center { text-align: center; }
.text-muted   { color: var(--text-muted); }

/* ── 5. Header & Navigation ───────────────────────────────── */
.site-header {
  position: sticky;
  top: 0;
  z-index: 200;
  height: var(--header-h);
  background: rgba(26, 15, 10, 0.90);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}

.site-header .container {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-2);
}

/* Logo */
.site-logo {
  display: flex;
  align-items: center;
  gap: var(--sp-1);
  flex-shrink: 0;
  color: var(--text);
  font-weight: 700;
  font-size: 1.1rem;
  letter-spacing: 0.02em;
}
.site-logo:hover { color: var(--accent-hover); }
.site-logo img  { height: 40px; width: auto; }

/* Desktop nav */
.main-nav {
  display: flex;
  align-items: center;
  gap: var(--sp-1);
}

.main-nav > a,
.main-nav > .nav-dropdown > .nav-drop-btn {
  padding: 0.45rem 0.75rem;
  font-size: 0.875rem;
  font-weight: 500;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--text);
  border-radius: var(--radius-sm);
  border: none;
  background: none;
  cursor: pointer;
  transition: color var(--trans), background var(--trans);
  white-space: nowrap;
}
.main-nav > a:hover,
.main-nav > .nav-dropdown > .nav-drop-btn:hover {
  color: var(--accent-hover);
  background: var(--accent-dim);
}
.main-nav > a.active {
  color: var(--accent);
  border-bottom: 2px solid var(--accent);
}

/* Dropdown */
.nav-dropdown {
  position: relative;
}
.nav-drop-btn {
  display: flex;
  align-items: center;
  gap: 4px;
}
.nav-drop-btn .chevron {
  width: 10px;
  height: 10px;
  border-right: 2px solid currentColor;
  border-bottom: 2px solid currentColor;
  transform: rotate(45deg) translateY(-2px);
  transition: transform var(--trans);
  display: inline-block;
}
.nav-dropdown.open .chevron,
.nav-dropdown:focus-within .chevron {
  transform: rotate(225deg) translateY(-2px);
}

.nav-drop-menu {
  display: none;
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  min-width: 200px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--sp-1) 0;
  box-shadow: 0 8px 24px rgba(0,0,0,0.5);
  z-index: 300;
}
.nav-dropdown:hover .nav-drop-menu,
.nav-dropdown.open .nav-drop-menu {
  display: block;
}
.nav-drop-menu a {
  display: block;
  padding: 0.6rem 1.1rem;
  font-size: 0.875rem;
  color: var(--text);
  transition: background var(--trans), color var(--trans);
}
.nav-drop-menu a:hover {
  background: var(--accent-dim);
  color: var(--accent-hover);
}

/* Hamburger toggle – hidden on desktop */
.menu-toggle {
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  background: none;
  cursor: pointer;
  gap: 5px;
  padding: 0;
  flex-shrink: 0;
}
.menu-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: transform 0.3s ease, opacity 0.3s ease;
}
.menu-toggle.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.menu-toggle.active span:nth-child(2) { opacity: 0; }
.menu-toggle.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* ── 6. Hero Section ──────────────────────────────────────── */
.hero {
  background: var(--bg-dark);
  min-height: calc(100vh - var(--header-h));
  display: flex;
  align-items: center;
  padding: var(--sp-8) 0;
  position: relative;
  overflow: hidden;
}

/* SVG background graphic — blue tones blend into dark background via screen */
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image: url('../images/bg_graphic_smol-2.svg');
  background-size: cover;
  background-position: center center;
  background-repeat: no-repeat;
  mix-blend-mode: screen;
  opacity: 0.18;
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 680px;
}

.hero-label {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  border: 1px solid var(--accent-border);
  border-radius: 100px;
  padding: 0.3rem 0.9rem;
  margin-bottom: var(--sp-3);
  background: var(--accent-dim);
}

.hero h1 {
  color: var(--text);
  margin-bottom: var(--sp-2);
}

.hero h1 em {
  font-style: normal;
  color: var(--accent);
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-3);
  margin: var(--sp-3) 0 var(--sp-4);
}

.hero-meta-item {
  display: flex;
  align-items: center;
  gap: var(--sp-1);
  color: var(--text-muted);
  font-size: 0.95rem;
}
.hero-meta-item svg { color: var(--accent); flex-shrink: 0; }

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-2);
}

/* ── 7. Buttons ───────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-1);
  padding: 0.7rem 1.6rem;
  font-size: 0.9rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  border-radius: var(--radius);
  border: 2px solid transparent;
  cursor: pointer;
  text-decoration: none;
  transition: background var(--trans), color var(--trans), border-color var(--trans), transform var(--trans), box-shadow var(--trans);
  white-space: nowrap;
}
.btn:hover { transform: translateY(-2px); }
.btn:active { transform: translateY(0); }

.btn-primary {
  background: var(--accent);
  color: var(--text-on-accent);
  border-color: var(--accent);
}
.btn-primary:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  color: var(--text-on-accent);
  box-shadow: 0 4px 16px rgba(192,67,43,0.4);
}

.btn-outline {
  background: transparent;
  color: var(--text);
  border-color: var(--border-subtle);
}
.btn-outline:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-dim);
}

.btn-sm { padding: 0.45rem 1rem; font-size: 0.8rem; }

/* ── 8. Cards ─────────────────────────────────────────────── */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--sp-3);
  transition: border-color var(--trans), box-shadow var(--trans), transform var(--trans);
}
.card:hover {
  border-color: var(--accent);
  box-shadow: 0 4px 20px rgba(192,67,43,0.15);
  transform: translateY(-3px);
}

.card-accent-left {
  border-left: 4px solid var(--accent);
}

/* Date / key-dates cards */
.date-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--sp-3);
  text-align: center;
}
.date-card .date-label {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: var(--sp-1);
}
.date-card .date-value {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 0.25rem;
}
.date-card .date-desc {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* Speaker / name cards */
.speaker-item {
  padding: var(--sp-2) var(--sp-3);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color var(--trans);
}
.speaker-item:hover { border-color: var(--accent); }
.speaker-item .speaker-name {
  font-weight: 600;
  color: var(--accent);
  font-size: 1rem;
  margin-bottom: 0.2rem;
}
.speaker-item .speaker-affil {
  font-size: 0.875rem;
  color: var(--text-muted);
}

/* ── 9. Program / Schedule ────────────────────────────────── */
.tab-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-1);
  margin-bottom: var(--sp-4);
  border-bottom: 2px solid var(--border);
  padding-bottom: var(--sp-1);
}
.tab-btn {
  padding: 0.5rem 1.2rem;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-muted);
  background: transparent;
  border: none;
  border-bottom: 3px solid transparent;
  cursor: pointer;
  transition: color var(--trans), border-color var(--trans);
  margin-bottom: -2px;
}
.tab-btn:hover { color: var(--text); }
.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.tab-day-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text);
  padding: var(--sp-3) 0 var(--sp-2);
  border-bottom: 1px solid var(--border);
  margin-bottom: var(--sp-3);
}

.tab-panel { display: none; }
.tab-panel.active { display: block; }

.schedule-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}
.schedule-table th {
  text-align: left;
  padding: 0.6rem 1rem;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-muted);
  border-bottom: 2px solid var(--border);
}
.schedule-table td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border-subtle);
  color: var(--text);
  vertical-align: top;
}
.schedule-table tr:last-child td { border-bottom: none; }
.schedule-table .time-col {
  width: 120px;
  color: var(--accent);
  font-weight: 600;
  font-size: 0.875rem;
  white-space: nowrap;
}
.schedule-table tr.session-break td {
  background: var(--accent-dim);
  color: var(--text-muted);
  font-style: italic;
  font-size: 0.875rem;
}
.schedule-table .talk-speaker { font-size: 0.875rem; color: var(--text-muted); }
.schedule-table .talk-body {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 0.25rem;
}
.schedule-table .talk-title { font-weight: 500; font-size: 0.9rem; flex: 1 1 auto; }

.abstract-btn {
  display: inline-block;
  flex-shrink: 0;
  padding: 0.15rem 0.65rem;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  border-radius: 100px;
  border: 1px solid var(--accent-border);
  background: var(--accent-dim);
  color: var(--accent);
  transition: background var(--trans), color var(--trans), border-color var(--trans);
  white-space: nowrap;
}
.abstract-btn:hover {
  background: var(--accent);
  color: var(--text-on-accent);
  border-color: var(--accent);
}

/* ── 10. Info / Callout Boxes ─────────────────────────────── */
.callout {
  background: var(--accent-dim);
  border: 1px solid var(--accent-border);
  border-left: 4px solid var(--accent);
  border-radius: var(--radius);
  padding: var(--sp-3);
  margin: var(--sp-3) 0;
}
.callout-title {
  font-weight: 700;
  color: var(--accent);
  margin-bottom: var(--sp-1);
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

/* ── 11. Fee Table ────────────────────────────────────────── */
.fee-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}
.fee-table th {
  background: var(--bg-dark);
  padding: 0.75rem 1rem;
  text-align: left;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  border-bottom: 2px solid var(--border);
}
.fee-table td {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border-subtle);
  color: var(--text);
}
.fee-table tr:last-child td { border-bottom: none; }
.fee-table .fee-amount {
  font-weight: 700;
  color: var(--accent);
}

/* ── 12. Form ─────────────────────────────────────────────── */
.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  margin-bottom: var(--sp-3);
}
.form-label {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
}
.form-input,
.form-textarea,
.form-select {
  background: var(--bg-dark);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  padding: 0.65rem 0.9rem;
  font-size: 0.9rem;
  font-family: inherit;
  transition: border-color var(--trans);
  width: 100%;
}
.form-input:focus,
.form-textarea:focus,
.form-select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(192, 67, 43, 0.15);
}
.form-textarea { resize: vertical; min-height: 120px; }
.form-error {
  font-size: 0.8rem;
  color: var(--accent);
  display: none;
}
.form-error.visible { display: block; }

/* ── 13. Footer ───────────────────────────────────────────── */
.site-footer {
  background: var(--bg-dark);
  border-top: 1px solid var(--border);
  padding: var(--sp-8) 0 var(--sp-4);
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: var(--sp-6);
  margin-bottom: var(--sp-6);
}

.footer-brand .site-logo { margin-bottom: var(--sp-2); }
.footer-brand p { font-size: 0.875rem; color: var(--text-muted); }

.footer-col h4 {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: var(--sp-2);
}
.footer-col p,
.footer-col address {
  font-size: 0.875rem;
  color: var(--text-muted);
  font-style: normal;
  line-height: 1.7;
}
.footer-col ul li {
  margin-bottom: 0.4rem;
}
.footer-col ul a {
  font-size: 0.875rem;
  color: var(--text-muted);
  transition: color var(--trans);
}
.footer-col ul a:hover { color: var(--accent-hover); }

.footer-bottom {
  border-top: 1px solid var(--border-subtle);
  padding-top: var(--sp-3);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: var(--sp-2);
  font-size: 0.8rem;
  color: var(--text-muted);
}
.footer-bottom a { color: var(--text-muted); }
.footer-bottom a:hover { color: var(--accent-hover); }

/* ── 14. Page Hero (inner pages) ──────────────────────────── */
.page-hero {
  background: var(--bg-dark);
  padding: var(--sp-8) 0 var(--sp-6);
  border-bottom: 1px solid var(--border);
}
.page-hero h1 { margin-bottom: var(--sp-2); }
.page-hero .breadcrumb {
  font-size: 0.825rem;
  color: var(--text-muted);
  margin-bottom: var(--sp-2);
}
.page-hero .breadcrumb a { color: var(--text-muted); }
.page-hero .breadcrumb a:hover { color: var(--accent); }
.page-hero .breadcrumb .sep { margin: 0 0.4em; }

/* ── 15. Misc Utilities ───────────────────────────────────── */
.badge {
  display: inline-block;
  padding: 0.2rem 0.65rem;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  border-radius: 100px;
  background: var(--accent-dim);
  color: var(--accent);
  border: 1px solid var(--accent-border);
}

.divider {
  height: 1px;
  background: var(--border);
  margin: var(--sp-4) 0;
}

.placeholder-note {
  display: inline-block;
  background: rgba(255, 200, 0, 0.12);
  border: 1px dashed rgba(255, 200, 0, 0.4);
  border-radius: var(--radius-sm);
  color: #ffe066;
  padding: 0.15rem 0.5rem;
  font-size: 0.85em;
  font-family: var(--font-mono);
}

/* Partners strip */
.partners-strip {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: var(--sp-4);
  padding: var(--sp-4) 0;
  opacity: 0.7;
}
.partner-logo {
  display: flex;
  align-items: center;
  justify-content: center;
}
.partner-logo img {
  height: 36px;
  width: auto;
  opacity: 0.75;
  transition: opacity var(--trans);
}
.partner-logo:hover img { opacity: 1; }

.partner-logo--placeholder {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-muted);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius);
  padding: 0.5rem 1.2rem;
}

/* ── 16. Media Queries ────────────────────────────────────── */

/* Tablet / mobile nav breakpoint */
@media (max-width: 900px) {
  .menu-toggle { display: flex; }

  .main-nav {
    display: none;
    position: absolute;
    top: var(--header-h);
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--bg-dark);
    border-bottom: 2px solid var(--border);
    z-index: 199;
    padding: var(--sp-2) 0;
  }
  .main-nav.open { display: flex; }

  .main-nav > a,
  .main-nav > .nav-dropdown > .nav-drop-btn {
    padding: 0.85rem var(--sp-3);
    border-radius: 0;
    font-size: 0.95rem;
    border-bottom: 1px solid var(--border-subtle);
    width: 100%;
    text-align: left;
  }

  .nav-dropdown { width: 100%; }
  .nav-drop-menu {
    position: static;
    border-radius: 0;
    border: none;
    border-top: 1px solid var(--border-subtle);
    background: rgba(0,0,0,0.2);
    box-shadow: none;
    padding: 0;
  }
  .nav-drop-menu a {
    padding: 0.75rem var(--sp-4);
    font-size: 0.9rem;
    border-bottom: 1px solid var(--border-subtle);
  }

  /* Keep dropdown always visible inside mobile menu when parent is open */
  .nav-dropdown .nav-drop-menu { display: none; }
  .nav-dropdown.open .nav-drop-menu { display: block; }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: var(--sp-4);
  }

  .grid-2, .grid-3 {
    grid-template-columns: 1fr;
  }
}

/* Small phones */
@media (max-width: 480px) {
  :root {
    --sp-8: 2.5rem;
    --sp-6: 2rem;
  }
  .hero { min-height: auto; padding: var(--sp-6) 0; }
  .hero-meta { flex-direction: column; gap: var(--sp-1); }
  .hero-actions { flex-direction: column; }
  .hero-actions .btn { width: 100%; justify-content: center; }
  .tab-bar { overflow-x: auto; flex-wrap: nowrap; }
  .schedule-table { font-size: 0.8rem; }
  .schedule-table .time-col { width: 80px; }
}