/* ===================================================================
   SkyDeLake — design tokens
   A lake at night, charted like a sky: deep teal ground, copper dawn
   accent, reed-green secondary. Serif display for headlines, grotesk
   body, monospace for metadata/code — like coordinates in a field
   journal.
   =================================================================== */

:root {
  --accent-math:      #5DA3C9; /* celestial blue — mathematics */
  --accent-math-soft: rgba(93,163,201,0.16);
  --bg:          #0F2027;
  --bg-alt:      #122A32;
  --surface:     #18343C;
  --surface-2:   #1E3F48;
  --border:      rgba(232, 241, 240, 0.12);
  --border-soft: rgba(232, 241, 240, 0.06);

  --text:        #E8F1F0;
  --text-muted:  #9FB4B0;
  --text-faint:  #6E8884;

  --accent:      #D98E4A; /* copper dawn */
  --accent-soft: rgba(217, 142, 74, 0.16);
  --accent-2:    #7FA68C; /* reed green */
  --accent-2-soft: rgba(127, 166, 140, 0.16);

  --font-display: 'Fraunces', Georgia, serif;
  --font-body:    'IBM Plex Sans', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono:    'IBM Plex Mono', 'SFMono-Regular', Menlo, monospace;

  --measure: 68ch;
  --radius: 4px;
  --shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

img { max-width: 100%; display: block; }

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

@media (prefers-reduced-motion: reduce) {
  * { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
}

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

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.15;
  margin: 0 0 0.5em;
  color: var(--text);
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5em;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-2);
}
.eyebrow::before {
  content: '';
  width: 1.1em;
  height: 1px;
  background: var(--accent-2);
}

.container {
  max-width: 1180px;
  margin: 0 auto;
  padding: 0 24px;
}

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

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(15, 32, 39, 0.88);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-soft);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-display);
  font-size: 1.35rem;
  font-weight: 600;
  color: var(--text);
}
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 30px;
  height: 30px;
  flex-shrink: 0;
}
.brand small {
  font-family: var(--font-mono);
  font-size: 0.62rem;
  letter-spacing: 0.08em;
  color: var(--text-faint);
  text-transform: uppercase;
  margin-left: 2px;
}

.main-nav { display: flex; align-items: center; gap: 28px; }
.main-nav a {
  color: var(--text-muted);
  font-size: 0.94rem;
  font-weight: 500;
}
.main-nav a:hover, .main-nav a.active { color: var(--text); text-decoration: none; }

.nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  padding: 8px 10px;
  cursor: pointer;
}

@media (max-width: 780px) {
  .nav-toggle { display: block; }
  .main-nav {
    position: absolute;
    top: 72px; left: 0; right: 0;
    background: var(--bg-alt);
    border-bottom: 1px solid var(--border-soft);
    flex-direction: column;
    align-items: flex-start;
    padding: 18px 24px 24px;
    gap: 16px;
    display: none;
  }
  .main-nav.open { display: flex; }
}

/* ---------------- Buttons / pills ---------------- */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  padding: 11px 20px;
  border-radius: var(--radius);
  border: 1px solid var(--accent);
  color: var(--accent);
  background: transparent;
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease;
}
.btn:hover { background: var(--accent); color: #0F2027; text-decoration: none; }
.btn.solid { background: var(--accent); color: #0F2027; }
.btn.solid:hover { background: #c87f3c; }
.btn.ghost { border-color: var(--border); color: var(--text-muted); }
.btn.ghost:hover { background: var(--surface); color: var(--text); }
.btn.small { padding: 7px 14px; font-size: 0.74rem; }
.btn.danger { border-color: #c1554a; color: #e08074; }
.btn.danger:hover { background: #c1554a; color: #fff; }

.pill {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  padding: 4px 10px;
  border-radius: 100px;
  border: 1px solid var(--border);
  color: var(--text-muted);
}
.pill.type-tutorial { border-color: var(--accent-2); color: var(--accent-2); }
.pill.type-blog { border-color: var(--accent); color: var(--accent); }
.pill.subject-mathematics { border-color: var(--accent-math); color: var(--accent-math); }
.filters a.pill.active.math { background: var(--accent-math-soft); border-color: var(--accent-math); color: var(--accent-math); }

.tag-row { display: flex; flex-wrap: wrap; gap: 8px; }
.tag-row a.pill:hover { background: var(--surface); text-decoration: none; }

/* ---------------- Hero ---------------- */

.hero {
  position: relative;
  padding: 84px 0 96px;
  overflow: hidden;
  border-bottom: 1px solid var(--border-soft);
}

.hero .container {
  position: relative;
  z-index: 2;
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  gap: 48px;
  align-items: center;
}

@media (max-width: 880px) {
  .hero .container { grid-template-columns: 1fr; }
}

.hero h1 {
  font-size: clamp(2.3rem, 4.4vw, 3.6rem);
  letter-spacing: -0.01em;
}
.hero h1 em {
  font-style: italic;
  color: var(--accent);
}
.hero p.lede {
  color: var(--text-muted);
  font-size: 1.08rem;
  max-width: 46ch;
  margin: 18px 0 28px;
}
.hero-actions { display: flex; gap: 14px; flex-wrap: wrap; }

.constellation-wrap {
  position: relative;
  min-height: 320px;
}
.constellation-wrap svg { width: 100%; height: auto; }
.constellation-wrap .star { fill: var(--text); }
.constellation-wrap .star.lit { fill: var(--accent); }
.constellation-wrap line { stroke: var(--border); stroke-width: 1; }
.constellation-wrap .node-label {
  font-family: var(--font-mono);
  font-size: 9px;
  fill: var(--text-faint);
}

/* ---------------- Section headers ---------------- */

.section-head {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 24px;
  margin: 0 0 28px;
  flex-wrap: wrap;
}
.section-head h2 { font-size: 1.7rem; margin: 6px 0 0; }
.section-head .see-all { font-family: var(--font-mono); font-size: 0.82rem; }

section.block { padding: 72px 0; }
section.block.alt { background: var(--bg-alt); }

/* ---------------- Cards / grid ---------------- */

.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
@media (max-width: 980px) { .grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 660px) { .grid { grid-template-columns: 1fr; } }

.card {
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform 0.15s ease, border-color 0.15s ease;
}
.card:hover { transform: translateY(-3px); border-color: var(--border); }
.card .thumb {
  aspect-ratio: 16/9;
  background: var(--surface-2) center/cover no-repeat;
  position: relative;
}
.card .thumb .play {
  position: absolute; inset: 0;
  display: flex; align-items: center; justify-content: center;
}
.card .thumb .play span {
  width: 44px; height: 44px; border-radius: 50%;
  background: rgba(15,32,39,0.7);
  border: 1px solid var(--accent);
  display: flex; align-items: center; justify-content: center;
  color: var(--accent);
}
.card .body { padding: 20px 22px 24px; display: flex; flex-direction: column; gap: 10px; flex: 1; }
.card .meta {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  color: var(--text-faint);
  display: flex; gap: 10px; align-items: center; flex-wrap: wrap;
}
.card h3 { font-size: 1.18rem; }
.card h3 a { color: var(--text); }
.card h3 a:hover { color: var(--accent); text-decoration: none; }
.card p.excerpt { color: var(--text-muted); font-size: 0.92rem; margin: 0; flex: 1; }

/* ---------------- Listing pages ---------------- */

.page-head {
  padding: 56px 0 32px;
  border-bottom: 1px solid var(--border-soft);
}
.page-head h1 { font-size: 2.3rem; }
.page-head p { color: var(--text-muted); max-width: 60ch; }

.filters {
  display: flex; flex-wrap: wrap; gap: 8px;
  margin: 24px 0 8px;
}
.filters a.pill.active { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); }

.pagination { display: flex; gap: 10px; justify-content: center; margin-top: 48px; }

.empty-state {
  text-align: center;
  padding: 80px 20px;
  color: var(--text-muted);
}
.empty-state h3 { color: var(--text); }

/* ---------------- Single post ---------------- */

.post-head { padding: 56px 0 8px; }
.post-head .pill { margin-bottom: 16px; }
.post-head h1 { font-size: clamp(1.9rem, 3.6vw, 2.7rem); max-width: 26ch; }
.post-head .meta {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text-faint);
  margin: 18px 0 0;
  display: flex; gap: 16px; flex-wrap: wrap;
}

.post-video {
  margin: 32px 0;
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border);
  background: #000;
}
.post-video .ratio { position: relative; padding-top: 56.25%; }
.post-video iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; }

.post-cover {
  margin: 32px 0;
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border-soft);
}

.post-body {
  max-width: var(--measure);
  margin: 0 auto;
  padding: 8px 0 16px;
  font-size: 1.06rem;
}
.post-body p { margin: 0 0 1.3em; color: #DCE9E7; }
.post-body h2 { font-size: 1.5rem; margin-top: 1.6em; }
.post-body h3 { font-size: 1.22rem; margin-top: 1.4em; }
.post-body ul, .post-body ol { margin: 0 0 1.3em; padding-left: 1.3em; color: #DCE9E7; }
.post-body li { margin-bottom: 0.4em; }
.post-body blockquote {
  margin: 1.6em 0; padding: 4px 0 4px 20px;
  border-left: 2px solid var(--accent);
  color: var(--text-muted); font-style: italic;
}
.post-body img { border-radius: var(--radius); margin: 1.6em 0; }
.post-body a { text-decoration: underline; text-underline-offset: 2px; }
.post-body code {
  font-family: var(--font-mono); font-size: 0.88em;
  background: var(--surface); padding: 0.15em 0.4em; border-radius: 3px;
}
.post-body pre {
  background: #0B181D; border: 1px solid var(--border-soft);
  border-radius: var(--radius); padding: 18px 20px; overflow-x: auto;
  margin: 1.6em 0;
}
.post-body pre code { background: none; padding: 0; font-size: 0.86rem; line-height: 1.55; }

.post-footer {
  max-width: var(--measure);
  margin: 40px auto 0;
  padding-top: 28px;
  border-top: 1px solid var(--border-soft);
}

.series-box {
  max-width: var(--measure);
  margin: 0 auto 40px;
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  padding: 20px 22px;
}
.series-box .eyebrow { margin-bottom: 12px; }
.series-box ol { list-style: none; margin: 0; padding: 0; counter-reset: step; }
.series-box li {
  counter-increment: step;
  font-family: var(--font-mono); font-size: 0.88rem;
  padding: 9px 0; border-top: 1px solid var(--border-soft);
  display: flex; gap: 10px; align-items: baseline;
}
.series-box li:first-child { border-top: none; }
.series-box li::before {
  content: counter(step, decimal-leading-zero);
  color: var(--text-faint);
}
.series-box li.current a { color: var(--accent); }
.series-box li a { color: var(--text-muted); }

/* ---------------- Forms (contact) ---------------- */

.form-field { margin-bottom: 18px; }
.form-field label {
  display: block; font-family: var(--font-mono); font-size: 0.78rem;
  letter-spacing: 0.04em; text-transform: uppercase; color: var(--text-muted);
  margin-bottom: 8px;
}
.form-field input, .form-field textarea, .form-field select {
  width: 100%; background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); color: var(--text); padding: 12px 14px;
  font-family: var(--font-body); font-size: 0.96rem;
}
.form-field textarea { min-height: 140px; resize: vertical; }
.form-field input:focus, .form-field textarea:focus, .form-field select:focus {
  outline: 2px solid var(--accent); outline-offset: 1px;
}
.alert { padding: 14px 16px; border-radius: var(--radius); margin-bottom: 20px; font-size: 0.92rem; }
.alert.success { background: var(--accent-2-soft); border: 1px solid var(--accent-2); color: var(--accent-2); }
.alert.error { background: rgba(193,85,74,0.12); border: 1px solid #c1554a; color: #e08074; }

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

.site-footer {
  border-top: 1px solid var(--border-soft);
  padding: 48px 0 36px;
  margin-top: 40px;
  background: var(--bg-alt);
}
.site-footer .container {
  display: flex; justify-content: space-between; align-items: center;
  flex-wrap: wrap; gap: 16px;
}
.site-footer p { color: var(--text-faint); font-size: 0.86rem; font-family: var(--font-mono); margin: 0; }
.site-footer .foot-links { display: flex; gap: 20px; }
.site-footer .foot-links a { color: var(--text-muted); font-size: 0.88rem; }

/* ---------------- About page ---------------- */

.prose { max-width: var(--measure); margin: 0 auto; padding: 56px 0 80px; }
.prose p { color: #DCE9E7; margin: 0 0 1.3em; font-size: 1.05rem; }
.prose h2 { margin-top: 1.4em; }

/* ── Nav auth ──────────────────────────────────────────────────────────── */

/* Chip + sign-in sit outside the nav, always visible */
.nav-user-wrap  { position: relative; flex-shrink: 0; }
.nav-signin-btn { flex-shrink: 0; }

/* On mobile: hide chip label/caret so only the initial circle shows */
@media (max-width: 780px) {
  .user-first, .chip-caret { display: none; }
  .user-chip { padding: 5px; }
}

/* Mobile auth section inside hamburger nav (hidden on desktop) */
.nav-mobile-auth {
  display: none;
  flex-direction: column;
  gap: 10px;
  width: 100%;
  padding-top: 12px;
  border-top: 1px solid var(--border-soft);
  margin-top: 4px;
}
.nav-mobile-who {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.04em;
  color: var(--text-faint);
  text-transform: uppercase;
}
.nav-mobile-auth a { color: var(--text-muted); font-size: 0.94rem; font-weight: 500; }
.nav-mobile-auth a:hover { color: var(--text); text-decoration: none; }
.nav-signout { color: #e08074 !important; }

@media (max-width: 780px) {
  .nav-mobile-auth { display: flex; }
}

/* User chip (desktop) */
.user-chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 4px 10px 4px 4px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 100px;
  cursor: pointer;
  color: var(--text);
  font-family: var(--font-body);
  font-size: 0.88rem;
  font-weight: 500;
  transition: border-color 0.18s, background 0.18s, box-shadow 0.18s;
}
.user-chip:hover {
  border-color: var(--accent);
  background: var(--surface-2);
  box-shadow: 0 0 0 3px rgba(217,142,74,0.12);
}
.user-chip[aria-expanded="true"] {
  border-color: var(--accent);
  background: var(--surface-2);
  box-shadow: 0 0 0 3px rgba(217,142,74,0.12);
}

.user-initial {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: linear-gradient(135deg, #D98E4A 0%, #b87030 100%);
  color: #0F2027;
  font-family: var(--font-mono);
  font-size: 0.74rem;
  font-weight: 700;
  flex-shrink: 0;
  letter-spacing: 0;
}

.chip-caret {
  color: var(--text-faint);
  transition: transform 0.2s ease;
  flex-shrink: 0;
}
.user-chip[aria-expanded="true"] .chip-caret { transform: rotate(180deg); }

/* Dropdown */
@keyframes dropIn {
  from { opacity: 0; transform: translateY(-6px) scale(0.98); }
  to   { opacity: 1; transform: translateY(0)   scale(1);    }
}

.user-dropdown {
  position: absolute;
  top: calc(100% + 10px);
  right: 0;
  min-width: 230px;
  background: var(--bg-alt);
  border: 1px solid rgba(232,241,240,0.15);
  border-radius: 8px;
  box-shadow: 0 20px 48px rgba(0,0,0,0.55), 0 0 0 1px rgba(232,241,240,0.04);
  padding: 6px 0;
  z-index: 200;
  animation: dropIn 0.16s ease;
}
.user-dropdown[hidden] { display: none; }

.user-drop-header {
  padding: 14px 16px 12px;
  border-bottom: 1px solid var(--border-soft);
  display: flex;
  align-items: center;
  gap: 12px;
}
.user-drop-avatar {
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background: linear-gradient(135deg, #D98E4A 0%, #b87030 100%);
  color: #0F2027;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  font-weight: 700;
  flex-shrink: 0;
}
.user-drop-info {
  display: flex;
  flex-direction: column;
  gap: 2px;
  min-width: 0;
}
.user-drop-name {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.user-drop-role {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--accent);
}

.user-drop-item {
  display: block;
  padding: 10px 16px;
  color: var(--text-muted);
  font-size: 0.88rem;
  font-weight: 500;
  text-decoration: none;
  transition: background 0.12s, color 0.12s;
}
.user-drop-item:hover { background: var(--surface); color: var(--text); text-decoration: none; }
.user-drop-divider { height: 1px; background: var(--border-soft); margin: 4px 0; }
.user-drop-signout { color: #e08074; }
.user-drop-signout:hover { background: rgba(193,85,74,0.1) !important; color: #e08074 !important; }

/* ── Auth / Sign-in page ───────────────────────────────────────────────── */

.auth-page {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg);
  padding: 32px 16px;
}

/* Card */
.auth-card {
  width: 100%;
  max-width: 400px;
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-top: 3px solid var(--accent);
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 24px 56px rgba(0,0,0,0.45);
}

/* Brand strip */
.auth-card-brand {
  padding: 22px 28px 20px;
  border-bottom: 1px solid var(--border-soft);
}
.auth-logo {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  text-decoration: none;
  color: var(--text);
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 600;
}
.auth-logo:hover { text-decoration: none; color: var(--text); }

/* Heading */
.auth-card-head {
  padding: 24px 28px 0;
}
.auth-title {
  font-family: var(--font-body);
  font-size: 1.35rem;
  font-weight: 600;
  margin: 0 0 4px;
  color: var(--text);
}
.auth-sub {
  font-size: 0.86rem;
  color: var(--text-muted);
  margin: 0;
}

/* Error banner */
.auth-error-banner {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 16px 28px 0;
  padding: 10px 14px;
  background: rgba(193,85,74,0.1);
  border: 1px solid rgba(193,85,74,0.35);
  border-radius: 5px;
  color: #e08074;
  font-size: 0.86rem;
}

/* Form */
.auth-form {
  padding: 20px 28px 24px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.auth-field {
  display: flex;
  flex-direction: column;
  gap: 5px;
}
.auth-field label {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-muted);
}
.auth-field input {
  width: 100%;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 5px;
  color: var(--text);
  padding: 9px 12px;
  font-family: var(--font-body);
  font-size: 0.92rem;
  transition: border-color 0.15s;
  box-sizing: border-box;
}
.auth-field input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(217,142,74,0.14);
}
.auth-input-err {
  border-color: #c1554a !important;
}
.auth-input-err:focus {
  box-shadow: 0 0 0 3px rgba(193,85,74,0.14) !important;
}

/* Sign-in button */
.auth-submit {
  width: 100%;
  padding: 10px 16px;
  margin-top: 4px;
  background: var(--accent);
  color: #0F2027;
  border: none;
  border-radius: 5px;
  font-family: var(--font-body);
  font-size: 0.92rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
}
.auth-submit:hover { background: #c87f3c; }
.auth-submit:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* Secondary "apply" row */
.auth-card-alt {
  padding: 0 28px 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  font-size: 0.84rem;
  color: var(--text-faint);
  border-bottom: 1px solid var(--border-soft);
  padding-bottom: 20px;
}
.auth-card-alt a {
  color: var(--accent);
  font-weight: 500;
}
.auth-card-alt a:hover { text-decoration: underline; }

/* Footer back link */
.auth-card-footer {
  padding: 14px 28px;
  text-align: center;
}
.auth-card-footer a {
  font-size: 0.82rem;
  color: var(--text-faint);
  font-family: var(--font-mono);
  letter-spacing: 0.02em;
}
.auth-card-footer a:hover { color: var(--text-muted); }

/* ── Contact page ───────────────────────────────────────────────────────── */

.contact-wrap { padding: 40px 0 80px; }

.contact-layout {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 48px;
}
@media (max-width: 820px) {
  .contact-layout { grid-template-columns: 1fr; }
  .contact-sidebar { order: 2; }
  .contact-form-col { order: 1; }
}

.contact-sidebar { display: flex; flex-direction: column; gap: 14px; }
.contact-info-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
}
.contact-info-title {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-faint);
  margin: 0 0 14px;
}
.contact-info-list {
  list-style: none;
  margin: 0; padding: 0;
  display: flex; flex-direction: column; gap: 12px;
}
.contact-info-list li { display: flex; flex-direction: column; gap: 2px; }
.contact-info-label {
  font-weight: 600;
  font-size: 0.84rem;
  color: var(--text);
}
.contact-info-list span:last-child { font-size: 0.82rem; color: var(--text-faint); }
.contact-info-card--note { font-size: 0.86rem; color: var(--text-muted); }
.contact-info-card--note p { margin: 0; }
.contact-info-card--note strong { color: var(--text); }

.contact-fields-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0 16px;
}
@media (max-width: 520px) { .contact-fields-row { grid-template-columns: 1fr; } }

.contact-success {
  display: flex;
  align-items: flex-start;
  gap: 18px;
  padding: 28px 24px;
  background: var(--surface);
  border: 1px solid var(--accent);
  border-radius: var(--radius);
  max-width: 540px;
  margin: 0 auto;
}
.contact-success-icon {
  width: 52px; height: 52px; flex-shrink: 0;
  background: var(--accent-soft);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  color: var(--accent);
}

/* ── Contributor application (join) page ─────────────────────────────── */

.join-page-head { border-bottom: 1px solid var(--border-soft); }
.join-page-head p { color: var(--text-muted); max-width: 58ch; margin: 8px 0 0; }

.join-layout {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 48px;
  padding: 48px 0 80px;
}
@media (max-width: 860px) {
  .join-layout { grid-template-columns: 1fr; }
  .join-sidebar { order: 2; }
  .join-form-col { order: 1; }
}

/* Sidebar */
.join-sidebar { display: flex; flex-direction: column; gap: 16px; }
.join-sidebar-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
}
.join-sidebar-title {
  font-size: 0.88rem;
  font-family: var(--font-mono);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-faint);
  margin: 0 0 14px;
}
.join-perk-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.join-perk-list li {
  display: flex;
  align-items: flex-start;
  gap: 9px;
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.45;
}
.join-perk-list svg { flex-shrink: 0; margin-top: 1px; }
.join-sidebar-note p { font-size: 0.86rem; color: var(--text-muted); margin: 0 0 6px; }
.join-sidebar-note p:last-child { margin: 0; }
.join-note-heading { font-weight: 600; color: var(--text) !important; }

/* Form sections */
.join-form { display: flex; flex-direction: column; gap: 0; }
.join-section {
  padding: 28px 0;
  border-bottom: 1px solid var(--border-soft);
}
.join-section:last-of-type { border-bottom: none; }
.join-section-header {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 20px;
}
.join-section-num {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  color: var(--accent);
  flex-shrink: 0;
}
.join-section-title { font-size: 1.1rem; margin: 0; }
.join-section-desc { color: var(--text-muted); font-size: 0.9rem; margin: -10px 0 18px; }
.join-optional { color: var(--text-faint); font-weight: 400; font-size: 0.82em; }
.req { color: var(--accent); }
.form-hint { display: block; color: var(--text-faint); font-size: 0.8rem; margin-top: 5px; }

.join-fields-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0 16px;
}
@media (max-width: 560px) { .join-fields-grid { grid-template-columns: 1fr; } }

/* Radio group */
.join-radio-group { display: flex; flex-direction: column; gap: 8px; margin-top: 4px; }
.join-radio {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  font-size: 0.92rem;
  color: var(--text-muted);
  padding: 10px 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color 0.15s, color 0.15s, background 0.15s;
  user-select: none;
}
.join-radio:hover { border-color: var(--accent); color: var(--text); }
.join-radio input { display: none; }
.join-radio-mark {
  width: 16px; height: 16px;
  border-radius: 50%;
  border: 1.5px solid var(--border);
  flex-shrink: 0;
  position: relative;
  transition: border-color 0.15s;
}
.join-radio-mark::after {
  content: '';
  position: absolute;
  inset: 3px;
  border-radius: 50%;
  background: var(--accent);
  opacity: 0;
  transition: opacity 0.15s;
}
.join-radio input:checked ~ .join-radio-mark { border-color: var(--accent); }
.join-radio input:checked ~ .join-radio-mark::after { opacity: 1; }
.join-radio:has(input:checked) { border-color: var(--accent); color: var(--text); background: var(--accent-soft); }

/* Topic checkboxes */
.join-topic-group { margin-bottom: 20px; }
.join-topic-group-label {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 10px;
}
.join-topic-group-label--math { color: var(--accent-math); }
.join-topic-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 8px;
}
@media (max-width: 560px) { .join-topic-grid { grid-template-columns: 1fr; } }

.join-topic-item { position: relative; }
.join-topic-item input[type="checkbox"] { position: absolute; opacity: 0; width: 0; height: 0; }
.join-topic-label {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 11px 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 0.88rem;
  color: var(--text-muted);
  transition: border-color 0.15s, color 0.15s, background 0.15s;
  user-select: none;
}
.join-topic-label:hover { border-color: var(--border); color: var(--text); background: var(--surface-2); }
.join-topic-item input:checked + .join-topic-tech {
  border-color: var(--accent); color: var(--accent); background: var(--accent-soft);
}
.join-topic-item input:checked + .join-topic-math {
  border-color: var(--accent-math); color: var(--accent-math); background: var(--accent-math-soft);
}
/* Checkbox icon */
.join-topic-check { flex-shrink: 0; color: var(--border); transition: color 0.15s; }
.join-topic-item input:checked + .join-topic-tech .join-topic-check { color: var(--accent); }
.join-topic-item input:checked + .join-topic-math .join-topic-check { color: var(--accent-math); }
.join-check-mark { opacity: 0; transition: opacity 0.15s; }
.join-topic-item input:checked + .join-topic-label .join-check-mark { opacity: 1; }

/* Submit row */
.join-submit-row { padding-top: 28px; }
.join-submit-btn { padding: 13px 28px; font-size: 0.92rem; }
.join-submit-note { color: var(--text-faint); font-size: 0.84rem; margin: 12px 0 0; }

/* Success state */
.join-success {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  padding: 80px 24px 100px;
  gap: 14px;
}
.join-success-icon {
  width: 72px; height: 72px;
  background: var(--surface);
  border: 1px solid var(--accent);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent);
}
.join-success h2 { margin: 0; }
.join-success p  { color: var(--text-muted); max-width: 42ch; margin: 0; }
.join-success strong { color: var(--text); }

/* ── Mathematics page ──────────────────────────────────────────────────── */

.math-hero {
  padding: 72px 0 56px;
  border-bottom: 1px solid var(--border-soft);
  position: relative;
  overflow: hidden;
}
.math-hero::before {
  content: '';
  position: absolute;
  top: -80px; right: -60px;
  width: 580px; height: 580px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(93,163,201,0.08) 0%, transparent 65%);
  pointer-events: none;
}
.math-hero-inner {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 48px;
  align-items: center;
}
@media (max-width: 760px) {
  .math-hero-inner { grid-template-columns: 1fr; }
  .math-hero-art   { display: none; }
}
.math-hero-art svg { display: block; }

.math-eyebrow { color: var(--accent-math) !important; }
.math-eyebrow::before { background: var(--accent-math) !important; }
.math-em { color: var(--accent-math); font-style: italic; }
.math-hero h1 { font-size: clamp(2.1rem, 3.8vw, 3.2rem); margin-bottom: 0.45em; }
.math-lead { color: var(--text-muted); max-width: 52ch; line-height: 1.72; margin: 0; }

/* Topic tiles band */
.math-topics-band {
  background: var(--bg-alt);
  border-bottom: 1px solid var(--border-soft);
  padding: 20px 0;
}
.math-topics {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 10px;
}
@media (max-width: 860px) { .math-topics { grid-template-columns: repeat(3, 1fr); } }
@media (max-width: 440px) { .math-topics { grid-template-columns: repeat(2, 1fr); } }

.math-topic {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  padding: 16px 8px 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.05em;
  text-align: center;
  text-decoration: none;
  transition: border-color 0.15s, color 0.15s, background 0.15s;
}
.math-topic:hover {
  border-color: var(--accent-math);
  color: var(--accent-math);
  background: rgba(93,163,201,0.07);
  text-decoration: none;
}
.math-topic.active {
  border-color: var(--accent-math);
  color: var(--accent-math);
  background: rgba(93,163,201,0.13);
  text-decoration: none;
}

/* Filter bar */
.math-filter-row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  padding: 22px 0 18px;
  border-bottom: 1px solid var(--border-soft);
}
.math-filter-divider {
  width: 1px;
  height: 18px;
  background: var(--border);
  flex-shrink: 0;
}
.pill.math-pill-active {
  background: var(--accent-math-soft);
  border-color: var(--accent-math);
  color: var(--accent-math);
}

/* Result count bar */
.math-result-banner {
  padding: 12px 0;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text-faint);
  border-bottom: 1px solid var(--border-soft);
  margin-bottom: 28px;
}
.math-result-banner strong { color: var(--text-muted); font-weight: 500; }
.math-result-banner a { color: var(--accent-math); }

/* Posts section */
.math-posts-section { padding: 32px 0 72px; }

/* Empty state */
.math-empty {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  padding: 80px 24px 100px;
  text-align: center;
}
.math-empty-icon {
  width: 72px;
  height: 72px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent-math);
  opacity: 0.75;
}
.math-empty h3 { color: var(--text-muted); margin: 0; font-size: 1.3rem; }
.math-empty p  { color: var(--text-faint);  margin: 0; max-width: 38ch; }
.math-empty a  { color: var(--accent-math); }