:root {
  --bg: #0b0d13;
  --bg-elev: #14161f;
  --bg-card: #181b25;
  --bg-card-2: #1e2230;
  --border: #262b39;
  --border-soft: rgba(255, 255, 255, 0.07);
  --text: #eceef4;
  --muted: #98a0b3;
  --accent: #5b9dff;
  --accent-strong: #3f7dff;
  --accent-soft: rgba(91, 157, 255, 0.16);
  --gold: #f3c677;
  --dsa: #4f9dff;
  --system-design: #34d399;
  --behavioral: #f59e0b;
  --misc: #a78bfa;
  --grad-warm: linear-gradient(135deg, #4f9dff 0%, #6a8bff 52%, #9d7bff 100%);
  --grad-warm-strong: linear-gradient(135deg, #3f7dff 0%, #5a78ff 52%, #8e6bff 100%);
  --radius: 14px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.45);
  --shadow-glow: 0 12px 34px rgba(91, 157, 255, 0.28);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: "Segoe UI", system-ui, -apple-system, Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg);
  background-image:
    radial-gradient(900px 520px at 12% -8%, rgba(91, 157, 255, 0.12), transparent 60%),
    radial-gradient(820px 480px at 92% 2%, rgba(124, 110, 240, 0.10), transparent 58%),
    radial-gradient(1000px 700px at 50% 118%, rgba(52, 130, 211, 0.07), transparent 60%);
  background-attachment: fixed;
  color: var(--text);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

::selection { background: rgba(91, 157, 255, 0.30); color: #fff; }

/* Refined scrollbar */
* { scrollbar-color: #2f3547 transparent; }

.wrap { width: min(1180px, 92vw); margin: 0 auto; }

/* Header */
.site-header {
  position: relative;
  background:
    radial-gradient(1200px 460px at 50% -170px, rgba(60, 90, 150, 0.35) 0%, transparent 62%),
    linear-gradient(180deg, rgba(255, 255, 255, 0.02), transparent 40%),
    var(--bg-elev);
  border-bottom: 1px solid var(--border);
}
.site-header::after {
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: -1px;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(91, 157, 255, 0.55), rgba(120, 110, 240, 0.45), transparent);
}
.site-header > .wrap { padding-bottom: 26px; }

/* Top nav (shared across pages) */
.top-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 14px;
  padding: 14px 0 18px;
}
.top-nav-brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 1.2rem;
  font-weight: 800;
  letter-spacing: -0.3px;
  color: var(--text);
  text-decoration: none;
}
.brand-logo {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  object-fit: cover;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.45);
}
.top-nav-links {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 10px;
}

/* Unified nav buttons — identical size, color-coded by purpose */
.nav-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  height: 40px;
  padding: 0 18px;
  border-radius: 999px;
  font-size: .92rem;
  font-weight: 600;
  text-decoration: none;
  white-space: nowrap;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text);
  transition: filter .15s, border-color .15s, transform .05s;
}
.nav-btn:hover { border-color: #3a4154; }
.nav-btn:active { transform: translateY(1px); }
.nav-btn.is-current { border-color: var(--accent); color: var(--accent); }
.nav-btn--linkedin { background: #0a66c2; border-color: #0a66c2; color: #fff; }
.nav-btn--linkedin:hover { filter: brightness(1.08); border-color: #0a66c2; }
.nav-btn--support {
  background: var(--grad-warm);
  background-size: 160% 160%;
  border: 1px solid transparent;
  color: #fff;
  font-weight: 700;
  box-shadow: 0 6px 16px rgba(91, 157, 255, 0.32);
  transition: transform .12s ease, box-shadow .15s ease, background-position .4s ease;
}
.nav-btn--support:hover {
  filter: none;
  background-position: 100% 0;
  transform: translateY(-1px);
  box-shadow: 0 9px 22px rgba(91, 157, 255, 0.46);
}
.nav-btn--support > span { filter: drop-shadow(0 1px 2px rgba(0,0,0,.25)); }
.nav-btn-ic {
  font-weight: 800;
  font-style: italic;
  background: #fff;
  color: #0a66c2;
  border-radius: 3px;
  padding: 0 3px;
  font-size: .78rem;
  line-height: 1.4;
}

/* Hero */
.hero { max-width: 760px; }
.brand { margin: 0; font-size: 2rem; letter-spacing: -0.5px; }
.hero-title {
  margin: 6px 0 10px;
  font-size: clamp(1.9rem, 4.4vw, 3rem);
  line-height: 1.08;
  letter-spacing: -0.5px;
  font-weight: 800;
}
.hero-grad {
  background: linear-gradient(100deg, var(--dsa) 0%, var(--accent) 38%, var(--misc) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.tagline { margin: 0 0 20px; color: var(--muted); font-size: 1.05rem; max-width: 640px; }
.hero-stats {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 20px;
  margin: 16px 0 0;
  padding: 0;
  color: var(--muted);
  font-size: .9rem;
}
.hero-stats li { display: inline-flex; align-items: center; gap: 6px; }
.hero-stats li + li::before {
  content: "";
  width: 4px;
  height: 4px;
  margin-right: 14px;
  border-radius: 50%;
  background: var(--border);
}
.hero-stats strong { color: var(--text); font-variant-numeric: tabular-nums; }
.hero-stats-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--system-design);
  box-shadow: 0 0 0 3px rgba(52, 211, 153, 0.18);
}
.search-box { position: relative; }
.search-icon {
  position: absolute;
  left: 17px;
  top: 50%;
  transform: translateY(-50%);
  font-size: .9rem;
  opacity: .65;
  pointer-events: none;
}
.search-box input {
  width: 100%;
  padding: 13px 18px 13px 44px;
  font-size: 1rem;
  color: var(--text);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 999px;
  outline: none;
  transition: border-color .15s, box-shadow .15s;
}
.search-box input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

/* Visible keyboard focus rings (mouse clicks stay clean via :focus-visible) */
a:focus-visible,
button:focus-visible,
.tab:focus-visible,
.chip:focus-visible,
.card:focus-visible,
.nav-btn:focus-visible,
.filters-toggle:focus-visible,
.donate-btn:focus-visible,
input:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 8px;
}
.search-box input:focus-visible {
  outline: none;
}

/* Floating support button */
.donate-btn {
  display: inline-flex;
  align-items: center;
  border: 2px solid rgba(255, 255, 255, 0.85);
  background: var(--grad-warm);
  background-size: 160% 160%;
  color: #fff;
  text-decoration: none;
  padding: 14px 23px;
  border-radius: 999px;
  font-weight: 700;
  box-shadow: var(--shadow-glow);
  transition: background-position .4s ease, transform .08s, box-shadow .2s;
}
.donate-btn:hover {
  background-position: 100% 0;
  box-shadow: 0 14px 30px rgba(91, 157, 255, 0.5);
}
.donate-btn:active { transform: translateY(1px); }
.donate-icon {
  color: #ffffff;
  margin-right: 7px;
  text-shadow: 0 0 5px rgba(0, 0, 0, 0.25);
}
.donate-btn--floating {
  position: fixed;
  right: 18px;
  bottom: 18px;
  z-index: 1000;
  border-color: rgba(200, 220, 255, 0.9);
  font-size: 1.05rem;
  padding: 14px 24px;
  animation: donate-pulse 2.8s ease-in-out infinite;
}
.donate-btn--floating:hover { animation-play-state: paused; transform: translateY(-2px); }
@keyframes donate-pulse {
  0%, 100% { box-shadow: 0 10px 26px rgba(91, 157, 255, 0.40), 0 0 0 0 rgba(91, 157, 255, 0.45); }
  50% { box-shadow: 0 10px 26px rgba(91, 157, 255, 0.40), 0 0 0 12px rgba(91, 157, 255, 0); }
}
@media (prefers-reduced-motion: reduce) {
  .donate-btn--floating { animation: none; }
  html { scroll-behavior: auto; }
}

/* Tabs */
.tabs {
  display: flex;
  flex-wrap: nowrap;
  gap: 10px;
  padding: 18px 0 6px;
  overflow-x: auto;
  scrollbar-width: thin;
  -webkit-overflow-scrolling: touch;
}
.tabs::-webkit-scrollbar { height: 6px; }
.tabs::-webkit-scrollbar-thumb { background: var(--border); border-radius: 999px; }
.tab {
  cursor: pointer;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text);
  padding: 9px 16px;
  border-radius: 999px;
  font-size: .95rem;
  white-space: nowrap;
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  transition: background .15s, border-color .15s, transform .05s;
}
.tab::before {
  content: "";
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex: 0 0 auto;
  background: var(--tab-color, var(--muted));
  transition: background .15s, opacity .15s;
}
.tab[data-cat="all"] { --tab-color: var(--accent); }
.tab[data-cat="dsa"] { --tab-color: var(--dsa); }
.tab[data-cat="system-design"] { --tab-color: var(--system-design); }
.tab[data-cat="behavioral"] { --tab-color: var(--behavioral); }
.tab[data-cat="misc"] { --tab-color: var(--misc); }
.tab:hover { border-color: #3a4154; }
.tab:active { transform: translateY(1px); }
.tab.is-active {
  background: var(--tab-color, var(--accent));
  border-color: var(--tab-color, var(--accent));
  color: #fff;
}
.tab[data-cat="system-design"].is-active,
.tab[data-cat="behavioral"].is-active { color: #0b0d12; }
.tab.is-active::before { background: currentColor; opacity: .5; }
.tab .count {
  font-size: .78rem;
  background: rgba(255, 255, 255, 0.12);
  padding: 1px 8px;
  border-radius: 999px;
  min-width: 22px;
  text-align: center;
}
.tab.is-active .count { background: rgba(0, 0, 0, 0.22); }

/* Filters */
.filters-bar { padding: 10px 0 4px; }
.filters-toggle {
  display: none;
  cursor: pointer;
  align-items: center;
  gap: 8px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text);
  padding: 9px 16px;
  border-radius: 999px;
  font-size: .9rem;
  font-weight: 600;
}
.filters-toggle.is-active { border-color: var(--accent); color: var(--accent); }
.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 14px 28px;
  padding: 4px 0;
}
.filter-group { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; }
.filter-label {
  font-size: .72rem;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--muted);
  margin-right: 2px;
}
.chip {
  cursor: pointer;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text);
  padding: 5px 12px;
  border-radius: 999px;
  font-size: .82rem;
  transition: background .15s, border-color .15s;
}
.chip:hover { border-color: #3a4154; }
.chip.is-active { background: #2d3344; border-color: #4b557a; }
.chip.diff-easy.is-active { background: #14532d; border-color: #1f7a45; }
.chip.diff-medium.is-active { background: #6b4e15; border-color: #a06f1d; }
.chip.diff-hard.is-active { background: #5f1d1d; border-color: #8a2b2b; }

/* Card pills (companies, topics, difficulty) */
.pills { display: flex; flex-wrap: wrap; gap: 5px; }
.pill {
  font-size: .68rem;
  padding: 2px 8px;
  border-radius: 999px;
  border: 1px solid var(--border);
  color: var(--muted);
  white-space: nowrap;
}
.pill.company { color: #cbd2e6; border-color: #39415a; }
.pill.topic { color: var(--dsa); border-color: #2c4a6b; }
.thumb .pill {
  position: absolute;
  top: 8px;
  left: 8px;
  font-weight: 700;
  color: #0b0d12;
  border: none;
}
.pill.diff-easy { background: #34d399; }
.pill.diff-medium { background: #f59e0b; }
.pill.diff-hard { background: #f87171; }

/* Status / grid */
.status { color: var(--muted); margin: 18px 0 6px; font-size: .9rem; }
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 20px;
  padding: 10px 0 50px;
}
.empty { text-align: center; color: var(--muted); padding: 60px 0; }

/* Card */
.card {
  background: linear-gradient(180deg, var(--bg-card-2), var(--bg-card));
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  text-decoration: none;
  color: inherit;
  transition: transform .14s ease, border-color .14s ease, box-shadow .14s ease;
}
.card:hover {
  transform: translateY(-5px);
  border-color: rgba(91, 157, 255, 0.45);
  box-shadow: 0 16px 36px rgba(0, 0, 0, 0.5), 0 0 0 1px rgba(91, 157, 255, 0.12);
}
.thumb {
  position: relative;
  aspect-ratio: 16 / 9;
  background: #11131b;
  overflow: hidden;
}
.thumb img { width: 100%; height: 100%; object-fit: cover; display: block; }
.thumb .play {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  font-size: 0;
  opacity: 0;
  background: rgba(0, 0, 0, 0.32);
  transition: opacity .18s;
}
.thumb .play::before {
  content: "▶";
  display: grid;
  place-items: center;
  width: 56px;
  height: 56px;
  font-size: 1.2rem;
  color: #fff;
  padding-left: 4px;
  background: var(--grad-warm);
  border-radius: 50%;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.45);
  transform: scale(.85);
  transition: transform .18s;
}
.card:hover .play { opacity: 1; }
.card:hover .play::before { transform: scale(1); }
.card-body { padding: 14px 16px 16px; display: flex; flex-direction: column; gap: 10px; flex: 1; }
.card-title {
  font-size: .98rem;
  font-weight: 600;
  margin: 0;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.card-meta { margin-top: auto; display: flex; align-items: center; justify-content: space-between; gap: 8px; }
.badge {
  font-size: .72rem;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 999px;
  color: #0b0d12;
}
.badge.dsa { background: var(--dsa); }
.badge.system-design { background: var(--system-design); }
.badge.behavioral { background: var(--behavioral); }
.badge.misc { background: var(--misc); }
.date { font-size: .76rem; color: var(--muted); }

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 22px 0;
  color: var(--muted);
  font-size: .85rem;
}
.site-footer a { color: var(--dsa); text-decoration: none; }
.site-footer a:hover { text-decoration: underline; }
.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  margin-top: 10px;
}
.footer-count {
  position: fixed;
  left: 16px;
  bottom: 16px;
  z-index: 60;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin: 0;
  padding: 7px 14px;
  color: var(--text);
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 999px;
  font-size: .82rem;
  box-shadow: 0 6px 20px rgba(0, 0, 0, .35);
  backdrop-filter: blur(6px);
}
.footer-count[hidden] {
  display: none;
}
@media (max-width: 560px) {
  .footer-count {
    left: 10px;
    bottom: 10px;
    padding: 6px 11px;
    font-size: .76rem;
  }
}
.footer-count strong {
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}

/* About page */
.about-hero-title { margin: 6px 0 4px; }
.about-main { padding: 32px 0 70px; }
.about-intro {
  display: flex;
  gap: 28px;
  align-items: center;
  flex-wrap: wrap;
}
.about-photo {
  width: 200px;
  height: 200px;
  object-fit: cover;
  border-radius: 50%;
  border: 4px solid var(--accent);
  box-shadow: var(--shadow);
  flex-shrink: 0;
}
.about-intro-text { flex: 1; min-width: 260px; }
.about-intro-text h2 { margin-top: 0; }
.about-intro-text p { color: var(--text); }

.about-quotes {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 16px;
  margin: 36px 0;
}
.quote {
  margin: 0;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: var(--radius);
  padding: 18px 20px;
  font-size: 1.02rem;
  font-style: italic;
  color: var(--text);
}

.about-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 26px;
  margin: 22px 0;
}
.about-card h2 { margin-top: 0; }
.about-card p { color: var(--text); margin-bottom: 0; }

/* ===== Support / donations ===== */
.about-support {
  position: relative;
  scroll-margin-top: 20px;
  border: 1px solid rgba(91, 157, 255, 0.28);
  background:
    radial-gradient(700px 320px at 100% -10%, rgba(91, 157, 255, 0.07), transparent 60%),
    radial-gradient(700px 320px at 0% 110%, rgba(91, 157, 255, 0.07), transparent 60%),
    var(--bg-card);
  padding: 30px 28px;
}
.support-head { max-width: 720px; }
.support-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 1.25rem;
  font-weight: 800;
  letter-spacing: .01em;
  background: var(--grad-warm);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 10px;
}
.support-eyebrow-ic {
  -webkit-text-fill-color: var(--accent);
  font-size: 1.1rem;
}
.about-support h2 {
  margin: 0 0 12px;
  font-size: 2.1rem;
  letter-spacing: -0.4px;
}
.support-lede { color: var(--muted); margin: 0; max-width: 640px; font-size: 1.04rem; }

.donate-tiers {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 18px;
  margin: 24px 0 18px;
  align-items: stretch;
}
.tier {
  position: relative;
  display: flex;
  flex-direction: column;
  text-decoration: none;
  background: linear-gradient(180deg, var(--bg-card-2), var(--bg-card));
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 28px 24px 24px;
  transition: transform .16s ease, border-color .16s ease, box-shadow .16s ease;
}
.tier:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow);
}
.tier--member {
  border: 1px solid rgba(91, 157, 255, 0.55);
  background:
    radial-gradient(460px 240px at 100% -50px, rgba(91, 157, 255, 0.16), transparent 70%),
    radial-gradient(420px 240px at 0% 120%, rgba(91, 157, 255, 0.12), transparent 70%),
    linear-gradient(165deg, rgba(124, 110, 240, 0.10), rgba(120, 110, 240, 0.04));
  box-shadow: 0 14px 38px rgba(0, 0, 0, 0.4), 0 0 0 1px rgba(91, 157, 255, 0.18);
}
.tier--member::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: 18px;
  padding: 1px;
  background: linear-gradient(160deg, rgba(91, 157, 255, 0.8), rgba(91, 157, 255, 0.35), transparent 60%);
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  pointer-events: none;
}
.tier--member:hover {
  box-shadow: 0 20px 48px rgba(0, 0, 0, 0.5), 0 0 0 1px rgba(91, 157, 255, 0.35);
}
.tier--once:hover { border-color: rgba(91, 157, 255, 0.5); }

.tier-badge {
  position: absolute;
  top: -13px;
  left: 24px;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 5px 13px;
  font-size: .72rem;
  font-weight: 800;
  letter-spacing: .03em;
  text-transform: uppercase;
  color: #2a1c05;
  background: linear-gradient(135deg, #f7d488, #f3c677 55%, #e8a94e);
  border-radius: 999px;
  box-shadow: 0 6px 16px rgba(91, 157, 255, 0.4);
  z-index: 1;
}
.tier-name {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--text);
}
.tier-price {
  display: flex;
  align-items: baseline;
  gap: 6px;
  margin: 6px 0 4px;
}
.tier-amount {
  font-size: 2.7rem;
  font-weight: 800;
  line-height: 1;
  color: var(--text);
  background: var(--grad-warm);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.tier-per { font-size: .95rem; color: var(--muted); font-weight: 600; }
.tier-desc { color: var(--muted); margin: 6px 0 14px; }
.tier-perks {
  list-style: none;
  padding: 0;
  margin: 0 0 20px;
  display: flex;
  flex-direction: column;
  gap: 9px;
}
.tier-perks li {
  position: relative;
  padding-left: 26px;
  color: var(--text);
  font-size: .92rem;
}
.tier-perks li::before {
  content: "✓";
  position: absolute;
  left: 0;
  top: 0;
  width: 18px;
  height: 18px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: .72rem;
  font-weight: 800;
  color: #fff;
  background: var(--system-design);
  border-radius: 50%;
}
.tier--member .tier-perks li::before {
  content: "★";
  background: linear-gradient(135deg, #f7d488, #e8a94e);
  color: #2a1c05;
}
.tier-cta {
  margin-top: auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 14px 20px;
  border-radius: 999px;
  font-weight: 800;
  font-size: 1rem;
  color: #fff;
  background: var(--grad-warm);
  background-size: 160% 160%;
  border: none;
  box-shadow: 0 10px 22px rgba(91, 157, 255, 0.35);
  transition: background-position .4s ease, box-shadow .2s;
}
.tier:hover .tier-cta { background-position: 100% 0; box-shadow: 0 14px 30px rgba(91, 157, 255, 0.5); }
.tier-cta--ghost {
  color: var(--text);
  background: transparent;
  border: 2px solid rgba(91, 157, 255, 0.55);
  box-shadow: none;
}
.tier:hover .tier-cta--ghost {
  background: var(--accent-soft);
  box-shadow: none;
}
.tier-secure {
  display: block;
  text-align: center;
  margin-top: 10px;
  font-size: .78rem;
  color: var(--muted);
}

/* Suggested amount chips (one-time gift) */
.amount-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 2px 0 18px;
}
.amount-chip {
  flex: 1 1 0;
  min-width: 64px;
  text-align: center;
  padding: 10px 8px;
  border-radius: 12px;
  font-weight: 800;
  font-size: 1rem;
  color: var(--text);
  background: var(--bg-elev);
  border: 1.5px solid var(--border);
  transition: border-color .14s, background .14s, transform .08s, color .14s;
}
.amount-chip span { display: block; font-size: .64rem; font-weight: 600; color: var(--muted); margin-top: 1px; letter-spacing: .02em; }
.amount-chip:hover {
  transform: translateY(-2px);
  border-color: rgba(91, 157, 255, 0.55);
  color: #fff;
}
.amount-chip--active {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: #fff;
}
.amount-chip--active span { color: var(--accent); }

.support-trust {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 10px 14px;
  margin: 0 0 26px;
  padding: 14px 16px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: .86rem;
  color: var(--muted);
}
.card-badges { display: inline-flex; gap: 7px; flex-wrap: wrap; }
.card-badge {
  display: inline-flex;
  align-items: center;
  padding: 4px 9px;
  font-size: .72rem;
  font-weight: 800;
  letter-spacing: .02em;
  color: var(--text);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 6px;
}
.card-badge--visa { color: #1a1f71; background: #fff; border-color: #fff; }
.card-badge--mc { color: #eb001b; background: #fff; border-color: #fff; }

.support-free {
  border-top: 1px solid var(--border);
  padding-top: 20px;
}
.support-free-label {
  display: block;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 12px;
}
.support-free-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.support-free-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 9px 16px;
  text-decoration: none;
  color: var(--text);
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 999px;
  font-size: .9rem;
  font-weight: 600;
  transition: border-color .12s, transform .12s;
}
.support-free-link:hover { border-color: var(--accent); transform: translateY(-2px); }
.support-free-ic { color: var(--accent); font-weight: 800; }

.about-back { margin-top: 30px; }
.about-back a { color: var(--dsa); text-decoration: none; }
.about-back a:hover { text-decoration: underline; }

/* Start Here roadmap */
.roadmap-main { padding: 32px 0 70px; }
.roadmap { list-style: none; counter-reset: phase; margin: 0; padding: 0; }
.phase {
  display: flex;
  gap: 18px;
  position: relative;
  padding: 0 0 28px 0;
}
.phase:not(:last-child)::before {
  content: "";
  position: absolute;
  left: 22px;
  top: 48px;
  bottom: 0;
  width: 2px;
  background: var(--border);
}
.phase-num {
  flex: 0 0 auto;
  width: 46px;
  height: 46px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-weight: 800;
  font-size: 1.1rem;
  color: #fff;
  background: var(--dsa);
  box-shadow: var(--shadow);
  z-index: 1;
}
.phase:nth-child(2) .phase-num { background: var(--dsa); }
.phase:nth-child(3) .phase-num { background: var(--system-design); }
.phase:nth-child(4) .phase-num { background: var(--behavioral); }
.phase:nth-child(5) .phase-num { background: var(--misc); }
.phase-body {
  flex: 1;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
}
.phase-body h2 { margin: 0 0 8px; font-size: 1.18rem; }
.phase-body p { color: var(--text); margin: 0 0 14px; }
.phase-links { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.phase-link {
  display: inline-flex;
  align-items: center;
  padding: 7px 14px;
  border-radius: 999px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  color: var(--text);
  text-decoration: none;
  font-size: .88rem;
  font-weight: 600;
}
.phase-link:hover { border-color: var(--dsa); color: #fff; }
.roadmap-cta { margin-top: 8px; text-align: center; }
.roadmap-cta .phase-links { justify-content: center; }

/* Resources hub */
.resources-main { padding: 32px 0 70px; }
.resources-main .about-card { margin-bottom: 22px; }
.resource-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px;
  margin-top: 16px;
}
.resource-tile {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 16px;
  border-radius: var(--radius);
  background: var(--bg-elev);
  border: 1px solid var(--border);
  text-decoration: none;
  transition: transform .12s ease, border-color .12s ease;
}
.resource-tile:hover { transform: translateY(-3px); border-color: var(--dsa); }
.resource-ic { font-size: 1.5rem; }
.resource-title { font-weight: 700; color: var(--text); }
.resource-sub { font-size: .82rem; color: var(--muted); }
.resource-note { color: var(--muted); font-size: .85rem; margin: 14px 0 0; }

/* Single video page */
.video-main { padding: 24px 0 70px; }
.breadcrumb { font-size: .85rem; color: var(--muted); margin-bottom: 16px; }
.breadcrumb a { color: var(--dsa); text-decoration: none; }
.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb span { margin: 0 6px; }
.breadcrumb-current { color: var(--muted); }
.video-article { max-width: 900px; margin: 0 auto; }
.video-embed {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  border-radius: var(--radius);
  overflow: hidden;
  background: #000;
  box-shadow: var(--shadow);
}
.video-embed iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
}
.video-title { margin: 20px 0 10px; font-size: 1.5rem; line-height: 1.3; }
.video-meta { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin-bottom: 12px; }
.video-meta .date { color: var(--muted); font-size: .85rem; }
.video-desc { color: var(--text); margin: 14px 0 22px; }
.video-cta { display: flex; flex-wrap: wrap; gap: 12px; margin: 22px 0; }
.video-back { margin-top: 18px; }
.video-back a { color: var(--dsa); text-decoration: none; }
.video-back a:hover { text-decoration: underline; }

@media (max-width: 720px) {
  .filters-toggle { display: inline-flex; }
  .filters {
    display: none;
    margin-top: 10px;
    width: 100%;
    flex-direction: column;
    gap: 12px;
  }
  .filters.is-open { display: flex; }
  .top-nav { padding: 12px 0 14px; }
  .top-nav-brand { font-size: 1.05rem; }
  .nav-btn { height: 36px; padding: 0 14px; font-size: .86rem; }
}

@media (max-width: 520px) {
  .brand { font-size: 1.6rem; }
  .tagline { font-size: .95rem; }
  .grid { grid-template-columns: 1fr 1fr; gap: 12px; }
  .card-title { font-size: .85rem; }
  .donate-btn--floating {
    right: 12px;
    bottom: 12px;
    font-size: .98rem;
    padding: 12px 20px;
  }
  .about-intro { flex-direction: column; text-align: center; }
  .about-photo { width: 160px; height: 160px; }
}