:root {
  --bg: #0f1220;
  --bg-2: #151a2d;
  --panel: #1b2138;
  --panel-2: #212a46;
  --border: #2c3556;
  --text: #e8ecf7;
  --muted: #9aa6c7;
  --accent: #14b8a6;
  --accent-2: #0ea5e9;
  --good: #3ecf8e;
  --warn: #f5b95a;
  --bad: #ff6b6b;
  --radius: 14px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
  --speed: 220ms;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f4f6fc;
    --bg-2: #eef1fb;
    --panel: #ffffff;
    --panel-2: #f5f7ff;
    --border: #dfe4f2;
    --text: #1a2036;
    --muted: #5a6488;
    --shadow: 0 10px 30px rgba(30, 40, 90, 0.12);
  }
}

* { box-sizing: border-box; }

html, body { margin: 0; padding: 0; }

body {
  font-family: "Segoe UI", system-ui, -apple-system, Roboto, Helvetica, Arial, sans-serif;
  background: radial-gradient(1200px 600px at 80% -10%, rgba(124, 108, 255, 0.18), transparent 60%),
              radial-gradient(1000px 500px at -10% 10%, rgba(91, 140, 255, 0.15), transparent 55%),
              var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: grid;
  grid-template-columns: 260px 1fr;
  grid-template-rows: auto 1fr auto;
  grid-template-areas:
    "top top"
    "side main"
    "side foot";
}

.skip-link {
  position: absolute; left: -999px; top: 0; z-index: 100;
  background: var(--accent); color: #fff; padding: 8px 14px; border-radius: 0 0 8px 0;
}
.skip-link:focus { left: 0; }

/* Top bar */
.topbar {
  grid-area: top;
  display: flex; align-items: center; gap: 18px;
  padding: 12px 20px;
  background: rgba(20, 26, 45, 0.7);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 30;
}
.brand { display: flex; align-items: center; gap: 10px; cursor: pointer; -webkit-user-select: none; user-select: none; }
.brand-logo {
  display: block; width: 40px; height: 40px; flex: 0 0 40px;
  border-radius: 10px;
  box-shadow: 0 6px 18px rgba(20, 184, 166, 0.28);
}
.brand-text { display: flex; flex-direction: column; font-size: 17px; line-height: 1; letter-spacing: 0.2px; }
.brand-text strong { color: var(--text); }
.brand-text span { margin-top: 4px; color: var(--accent); font-size: 10px; font-weight: 700; letter-spacing: 1.6px; text-transform: uppercase; }
.topbar-search { flex: 1; max-width: 640px; }
.topbar-search input {
  width: 100%; padding: 11px 16px; border-radius: 999px;
  border: 1px solid var(--border); background: var(--panel);
  color: var(--text); font-size: 14px; outline: none;
  transition: border-color var(--speed), box-shadow var(--speed);
}
.topbar-search input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(91, 140, 255, 0.25);
}
.nav-toggle {
  display: none; background: var(--panel); color: var(--text);
  border: 1px solid var(--border); border-radius: 10px; padding: 8px 12px; font-size: 18px; cursor: pointer;
}

/* Side nav */
.sidenav {
  grid-area: side;
  border-right: 1px solid var(--border);
  padding: 16px 12px;
  background: rgba(21, 26, 45, 0.5);
  display: flex; flex-direction: column;
  position: sticky; top: 61px; height: calc(100vh - 61px); overflow-y: auto;
}
.sidenav ul { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 4px; }
.sidenav button {
  width: 100%; text-align: left; background: transparent; color: var(--text);
  border: 1px solid transparent; border-radius: 10px; padding: 10px 12px;
  font-size: 14px; cursor: pointer;
  transition: background var(--speed), transform var(--speed), border-color var(--speed);
}
.sidenav button:hover { background: var(--panel); transform: translateX(2px); }
.sidenav button.active {
  background: linear-gradient(120deg, rgba(91,140,255,0.22), rgba(124,108,255,0.22));
  border-color: var(--border);
}
.sidenav-foot { margin-top: auto; padding: 12px; color: var(--muted); font-size: 11px; }

/* Content */
.content { grid-area: main; padding: 26px clamp(16px, 4vw, 44px); }
.footer {
  grid-area: foot; padding: 14px 24px; color: var(--muted); font-size: 12px;
  border-top: 1px solid var(--border); text-align: center;
}
.footer code { color: var(--accent); }

.view { animation: fadeUp var(--speed) ease both; }

/* Hero */
.hero {
  background: linear-gradient(135deg, rgba(91,140,255,0.16), rgba(124,108,255,0.12));
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 30px; margin-bottom: 24px; box-shadow: var(--shadow);
}
.hero h1 { margin: 0 0 8px; font-size: clamp(22px, 3.4vw, 34px); }
.hero p { margin: 0; color: var(--muted); max-width: 70ch; line-height: 1.6; }
.eyebrow { margin-bottom: 8px; color: var(--accent); font-size: 12px; font-weight: 800; letter-spacing: 1.8px; text-transform: uppercase; }

/* Stat cards */
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 14px; margin-bottom: 26px; }
.stat {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px; box-shadow: var(--shadow);
  transition: transform var(--speed), border-color var(--speed);
}
.stat:hover { transform: translateY(-3px); border-color: var(--accent); }
.stat .num { font-size: 30px; font-weight: 700; color: var(--accent); }
.stat .label { color: var(--muted); font-size: 13px; margin-top: 4px; }

/* Section titles */
.section-title { font-size: 18px; margin: 26px 0 14px; display: flex; align-items: center; gap: 10px; }
.section-title .pill { font-size: 12px; color: var(--muted); font-weight: 400; }

/* Mode cards grid (home) */
.mode-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 14px; }
.mode-card {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px; cursor: pointer; text-align: left;
  transition: transform var(--speed), border-color var(--speed), background var(--speed);
}
.mode-card:hover { transform: translateY(-4px); border-color: var(--accent); background: var(--panel-2); }
.mode-card .emoji { font-size: 24px; }
.mode-card h3 { margin: 8px 0 4px; font-size: 16px; }
.mode-card p { margin: 0; color: var(--muted); font-size: 13px; line-height: 1.5; }

/* Filters */
.filters { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 18px; }
.filters select {
  background: var(--panel); color: var(--text); border: 1px solid var(--border);
  border-radius: 10px; padding: 9px 12px; font-size: 13px; cursor: pointer;
}
.filters .count { margin-left: auto; color: var(--muted); font-size: 13px; align-self: center; }

/* Question list */
.q-list { display: grid; gap: 12px; }
.q-card {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px; box-shadow: var(--shadow); cursor: pointer;
  transition: transform var(--speed), border-color var(--speed);
}
.q-card:hover { transform: translateY(-2px); border-color: var(--accent); }
.q-card h3 { margin: 0 0 10px; font-size: 15.5px; line-height: 1.4; }
.q-card .meta { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }

/* Badges */
.badge {
  font-size: 11px; padding: 3px 9px; border-radius: 999px; border: 1px solid var(--border);
  color: var(--muted); white-space: nowrap;
}
.badge.cat { color: var(--accent); border-color: rgba(91,140,255,0.5); }
.badge.type { color: var(--accent-2); border-color: rgba(124,108,255,0.5); }
.badge.d-Beginner { color: var(--good); border-color: rgba(62,207,142,0.5); }
.badge.d-Intermediate { color: var(--warn); border-color: rgba(245,185,90,0.5); }
.badge.d-Advanced { color: #ff9d5c; border-color: rgba(255,157,92,0.5); }
.badge.d-Architect { color: var(--bad); border-color: rgba(255,107,107,0.5); }
.badge.lvl { color: var(--muted); }
.fav-btn {
  margin-left: auto; background: transparent; border: none; cursor: pointer;
  font-size: 18px; color: var(--muted); transition: transform var(--speed), color var(--speed);
}
.fav-btn:hover { transform: scale(1.2); }
.fav-btn.on { color: var(--warn); }

/* Detail / rendered markdown */
.detail {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: clamp(18px, 3vw, 32px); box-shadow: var(--shadow);
}
.detail .back { margin-bottom: 16px; }
.md h1 { font-size: 24px; margin: 0 0 14px; }
.md h2 {
  font-size: 18px; margin: 26px 0 10px; padding-bottom: 6px;
  border-bottom: 1px solid var(--border); color: var(--accent);
}
.md h3 { font-size: 15px; margin: 18px 0 8px; color: var(--accent-2); }
.md p, .md li { line-height: 1.7; color: var(--text); }
.md ul, .md ol { padding-left: 22px; }
.md blockquote {
  margin: 12px 0; padding: 10px 16px; border-left: 3px solid var(--accent);
  background: var(--panel-2); border-radius: 0 10px 10px 0; color: var(--muted);
}
.md code {
  background: var(--bg-2); padding: 2px 6px; border-radius: 6px;
  font-family: "Cascadia Code", Consolas, "Courier New", monospace; font-size: 13px;
}
.md pre {
  background: #0b0e1a; border: 1px solid var(--border); border-radius: 10px;
  padding: 14px 16px; overflow-x: auto; margin: 12px 0;
}
.md pre code { background: transparent; padding: 0; color: #d6e0ff; }
.md table { border-collapse: collapse; width: 100%; margin: 14px 0; font-size: 13.5px; }
.md th, .md td { border: 1px solid var(--border); padding: 8px 10px; text-align: left; }
.md th { background: var(--panel-2); }
.md a { color: var(--accent); }
.md hr { border: none; border-top: 1px solid var(--border); margin: 22px 0; }

/* Callouts (auto-styled by section) */
.callout { border-radius: 12px; padding: 2px 16px; margin: 14px 0; border: 1px solid var(--border); }
.callout.mistake { border-color: rgba(255,107,107,0.4); background: rgba(255,107,107,0.07); }
.callout.expect  { border-color: rgba(91,140,255,0.4); background: rgba(91,140,255,0.07); }
.callout.senior  { border-color: rgba(124,108,255,0.4); background: rgba(124,108,255,0.08); }
.callout.followup{ border-color: rgba(245,185,90,0.4); background: rgba(245,185,90,0.07); }

/* Interview / flip */
.interview-stage { max-width: 900px; margin: 0 auto; }
.flip-controls { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 16px; }
.btn {
  background: linear-gradient(120deg, var(--accent), var(--accent-2)); color: #fff;
  border: none; border-radius: 10px; padding: 11px 18px; font-size: 14px; cursor: pointer;
  transition: transform var(--speed), filter var(--speed);
}
.btn:hover { transform: translateY(-2px); filter: brightness(1.08); }
.btn.ghost { background: var(--panel); color: var(--text); border: 1px solid var(--border); }
.btn.good { background: linear-gradient(120deg, var(--good), #2fae77); }
.btn.bad  { background: linear-gradient(120deg, var(--bad), #e05555); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }

.reveal-hidden { filter: blur(7px); -webkit-user-select: none; user-select: none; transition: filter 400ms ease; }
.reveal-shown  { filter: none; }

.progress-track { height: 8px; background: var(--bg-2); border-radius: 999px; overflow: hidden; margin: 10px 0 20px; }
.progress-fill { height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent-2)); width: 0; transition: width 400ms ease; }

/* Mock setup form */
.form-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 14px; margin: 16px 0; }
.field label { display: block; font-size: 13px; color: var(--muted); margin-bottom: 6px; }
.field select, .field input {
  width: 100%; background: var(--panel); color: var(--text);
  border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px; font-size: 14px;
}

/* Score result */
.score-ring { font-size: 46px; font-weight: 700; color: var(--accent); }
.area-list { display: grid; gap: 8px; margin-top: 10px; }
.area-row { display: flex; align-items: center; gap: 10px; }
.area-row .bar { flex: 1; height: 8px; background: var(--bg-2); border-radius: 999px; overflow: hidden; }
.area-row .bar > span { display: block; height: 100%; background: var(--accent); }

.empty { color: var(--muted); padding: 30px; text-align: center; border: 1px dashed var(--border); border-radius: var(--radius); }

.tag-row { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 12px; }
.tag { font-size: 11px; color: var(--muted); background: var(--bg-2); padding: 3px 8px; border-radius: 6px; }

/* Animations */
@keyframes fadeUp { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
@keyframes spin { to { transform: rotate(360deg); } }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
  .reveal-hidden { filter: none; }
}

/* Responsive */
@media (max-width: 860px) {
  body { grid-template-columns: 1fr; grid-template-areas: "top" "main" "foot"; }
  .sidenav {
    position: fixed; top: 61px; left: 0; width: 250px; height: calc(100vh - 61px);
    z-index: 40; transform: translateX(-105%); transition: transform var(--speed);
    background: var(--bg-2);
  }
  .sidenav.open { transform: none; }
  .nav-toggle { display: inline-block; }
  .brand-text { display: none; }
}