:root {
  --bg: #0b1220;
  --bg-2: #111a2e;
  --panel: #15203a;
  --panel-2: #1b2a4a;
  --border: #243456;
  --text: #e6ecf7;
  --muted: #9aa7c2;
  --accent: #4f8cff;
  --accent-2: #38d6a0;
  --danger: #ff6b6b;
  --warn: #ffb86b;
  --ok: #38d6a0;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
  --radius: 14px;
  --radius-sm: 10px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }

body {
  font-family: 'Inter', system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
  background:
    radial-gradient(1200px 600px at 80% -10%, rgba(79, 140, 255, 0.18), transparent 60%),
    radial-gradient(1000px 500px at -10% 30%, rgba(56, 214, 160, 0.10), transparent 60%),
    linear-gradient(180deg, var(--bg) 0%, var(--bg-2) 100%);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

.container { max-width: 1100px; margin: 0 auto; padding: 0 20px; }

/* Topbar */
.topbar {
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: blur(12px);
  background: rgba(11, 18, 32, 0.6);
  border-bottom: 1px solid var(--border);
}
.topbar-inner {
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 20px;
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--text); }
.brand-mark {
  width: 32px; height: 32px; border-radius: 8px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  display: inline-grid; place-items: center; font-weight: 800; font-size: 13px;
  color: #0b1220;
}
.brand-text { font-weight: 700; letter-spacing: 0.3px; }
.topnav a { color: var(--muted); margin-left: 18px; text-decoration: none; font-weight: 500; }
.topnav a:hover { color: var(--text); }

/* Views */
.view { display: none; padding: 32px 0 80px; }
.view.active { display: block; }

/* Hero */
.hero { padding: 40px 0 20px; }
.eyebrow {
  display: inline-block; padding: 6px 12px;
  border-radius: 999px;
  background: rgba(79, 140, 255, 0.12);
  color: #b9d0ff; font-size: 12px; font-weight: 600;
  text-transform: uppercase; letter-spacing: 0.8px;
  border: 1px solid rgba(79, 140, 255, 0.3);
  margin-bottom: 16px;
}
.hero h1 {
  font-size: clamp(36px, 6vw, 64px);
  line-height: 1.05; margin: 0 0 14px;
  background: linear-gradient(180deg, #ffffff 0%, #c6d3f0 100%);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.lead { color: var(--muted); max-width: 760px; font-size: 18px; }
.small { font-size: 13px; }
.cta-row { display: flex; gap: 12px; flex-wrap: wrap; margin: 24px 0 8px; align-items: center; }
.hint { color: var(--muted); font-size: 14px; }

/* Buttons */
.btn {
  appearance: none; border: 0; cursor: pointer; font-family: inherit;
  padding: 12px 18px; border-radius: 10px; font-weight: 600; font-size: 15px;
  transition: transform 0.05s ease, background 0.2s ease, border-color 0.2s ease;
}
.btn:active { transform: translateY(1px); }
.btn-primary { background: linear-gradient(180deg, #5b96ff, #3b78e6); color: #fff; box-shadow: 0 8px 20px rgba(59, 120, 230, 0.35); }
.btn-primary:hover { background: linear-gradient(180deg, #6ea2ff, #4682f0); }
.btn-secondary { background: var(--panel); color: var(--text); border: 1px solid var(--border); }
.btn-secondary:hover { background: var(--panel-2); }
.btn-ghost { background: transparent; color: var(--muted); border: 1px solid var(--border); }
.btn-ghost:hover { color: var(--text); background: var(--panel); }
.btn[disabled] { opacity: 0.5; cursor: not-allowed; }

/* Categories */
.categories { margin-top: 48px; }
.categories h2 { margin-bottom: 18px; font-size: 24px; }
.cat-grid { display: grid; gap: 14px; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); }
.cat-card {
  background: linear-gradient(180deg, var(--panel) 0%, var(--panel-2) 100%);
  border: 1px solid var(--border);
  border-radius: var(--radius); padding: 18px;
  cursor: pointer; transition: transform 0.15s ease, border-color 0.15s ease;
  display: flex; flex-direction: column; gap: 8px;
}
.cat-card:hover { transform: translateY(-2px); border-color: rgba(79, 140, 255, 0.5); }
.cat-card h3 { margin: 0; font-size: 17px; }
.cat-card p { margin: 0; color: var(--muted); font-size: 14px; }
.cat-count { font-size: 12px; color: #b9d0ff; font-weight: 600; }

.about { margin-top: 56px; max-width: 820px; }
.about h2 { font-size: 22px; margin-bottom: 10px; }
.about p { color: var(--muted); }

/* Quiz */
.quiz-head {
  display: flex; align-items: center; justify-content: space-between;
  margin: 8px 0 12px; flex-wrap: wrap; gap: 12px;
}
.quiz-meta { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.pill {
  display: inline-block; padding: 6px 12px; border-radius: 999px;
  background: rgba(79, 140, 255, 0.12); border: 1px solid rgba(79, 140, 255, 0.3);
  color: #b9d0ff; font-size: 12px; font-weight: 600; letter-spacing: 0.5px;
}
.pill.alt { background: rgba(56, 214, 160, 0.10); border-color: rgba(56, 214, 160, 0.3); color: #b8f0d8; }
.pill.difficulty.easy { background: rgba(56, 214, 160, 0.10); border-color: rgba(56, 214, 160, 0.35); color: #b8f0d8; }
.pill.difficulty.medium { background: rgba(255, 184, 107, 0.10); border-color: rgba(255, 184, 107, 0.35); color: #ffd9aa; }
.pill.difficulty.hard { background: rgba(255, 107, 107, 0.10); border-color: rgba(255, 107, 107, 0.35); color: #ffb8b8; }
.pill.type.multi { background: rgba(180, 120, 255, 0.10); border-color: rgba(180, 120, 255, 0.35); color: #d6bbff; }
.pill.type.calc { background: rgba(120, 200, 255, 0.10); border-color: rgba(120, 200, 255, 0.35); color: #b4dcff; }
.quiz-score { color: var(--muted); }
.quiz-score strong { color: var(--text); }

.progress-bar {
  position: relative; height: 8px; background: var(--panel);
  border-radius: 999px; overflow: hidden; border: 1px solid var(--border);
  margin-bottom: 22px;
}
.progress-bar span {
  display: block; height: 100%; width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width 0.3s ease;
}

.question-card {
  background: linear-gradient(180deg, var(--panel) 0%, var(--panel-2) 100%);
  border: 1px solid var(--border);
  border-radius: var(--radius); padding: 28px; box-shadow: var(--shadow);
}
.question-card h2 { margin: 0 0 18px; font-size: 22px; line-height: 1.4; }

.question-image {
  margin: 0 0 18px; padding: 14px; border-radius: var(--radius-sm);
  background: rgba(255,255,255,0.03); border: 1px solid var(--border);
  display: flex; flex-direction: column; align-items: center; gap: 8px;
}
.question-image img { max-width: 100%; max-height: 320px; height: auto; border-radius: 8px; }
.question-image figcaption { font-size: 13px; color: var(--muted); }

.answers { list-style: none; padding: 0; margin: 0 0 16px; display: grid; gap: 10px; }
.answers li {
  background: var(--bg-2); border: 1px solid var(--border); border-radius: var(--radius-sm);
  padding: 14px 16px; cursor: pointer; display: flex; align-items: flex-start; gap: 12px;
  transition: border-color 0.15s ease, background 0.15s ease;
}
.answers li:hover { border-color: rgba(79, 140, 255, 0.5); }
.answers li .marker {
  flex: 0 0 28px; height: 28px; border-radius: 50%;
  background: var(--panel); border: 1px solid var(--border);
  display: grid; place-items: center; font-weight: 700; font-size: 13px;
}
.answers.multi li.checkbox .marker { border-radius: 6px; }
.answers li.selected { border-color: var(--accent); background: rgba(79, 140, 255, 0.08); }
.answers li.selected .marker { background: var(--accent); color: #0b1220; border-color: var(--accent); }
.answers li.correct { border-color: var(--ok); background: rgba(56, 214, 160, 0.10); }
.answers li.correct .marker { background: var(--ok); color: #0b1220; border-color: var(--ok); }
.answers li.wrong { border-color: var(--danger); background: rgba(255, 107, 107, 0.08); }
.answers li.wrong .marker { background: var(--danger); color: #0b1220; border-color: var(--danger); }
.answers li.missed { border-color: var(--warn); background: rgba(255, 184, 107, 0.08); }
.answers li.missed .marker { background: var(--warn); color: #0b1220; border-color: var(--warn); }
.answers li.locked { cursor: not-allowed; }

.calc-wrap { padding: 18px; border-radius: var(--radius-sm); background: rgba(255,255,255,0.03); border: 1px solid var(--border); }
.calc-label { display: block; margin-bottom: 8px; color: var(--muted); font-size: 14px; }
.calc-row { display: flex; align-items: center; gap: 10px; }
.calc-row input {
  flex: 1; font: 600 22px/1.2 'Inter', system-ui, sans-serif;
  padding: 12px 14px; border-radius: 10px; border: 1px solid var(--border);
  background: var(--bg-2); color: var(--text);
}
.calc-row input:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px rgba(79,140,255,0.2); }
.calc-row input.correct { border-color: var(--ok); box-shadow: 0 0 0 3px rgba(56,214,160,0.2); }
.calc-row input.wrong { border-color: var(--danger); box-shadow: 0 0 0 3px rgba(255,107,107,0.2); }
.calc-row input.invalid { border-color: var(--warn); }
.calc-unit { font-weight: 600; color: var(--muted); font-size: 16px; }
.calc-hint { margin: 10px 0 0; color: var(--muted); font-size: 13px; }
.calc-correct { margin: 12px 0 0; color: var(--text); }

.feedback {
  margin: 12px 0; padding: 14px 16px;
  border-radius: var(--radius-sm); border: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.02);
}
.feedback-text { margin: 0 0 6px; font-weight: 600; }
.feedback-text.ok { color: var(--ok); }
.feedback-text.bad { color: var(--danger); }
.explanation { margin: 0; color: var(--muted); font-size: 14px; }

.sources { margin-top: 12px; padding-top: 10px; border-top: 1px dashed var(--border); }
.sources h4 { margin: 0 0 6px; font-size: 13px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.5px; }
.sources ul { margin: 0; padding-left: 18px; }
.sources li { margin: 2px 0; font-size: 14px; }
.sources a { color: var(--accent-2); text-decoration: none; }
.sources a:hover { text-decoration: underline; }

.quiz-actions { display: flex; justify-content: space-between; align-items: center; margin-top: 18px; gap: 12px; flex-wrap: wrap; }
.right-actions { display: flex; gap: 10px; }

/* Results */
.results-card {
  background: linear-gradient(180deg, var(--panel) 0%, var(--panel-2) 100%);
  border: 1px solid var(--border);
  border-radius: var(--radius); padding: 36px; text-align: center;
  box-shadow: var(--shadow); margin-top: 24px;
}
.score-circle {
  width: 160px; height: 160px; border-radius: 50%;
  margin: 20px auto; display: grid; place-items: center;
  background: conic-gradient(var(--accent) var(--p, 0%), var(--panel) 0);
  position: relative;
}
.score-circle::before {
  content: ''; position: absolute; inset: 10px;
  background: var(--panel); border-radius: 50%;
}
.score-circle span { position: relative; font-size: 32px; font-weight: 800; }
.score-summary { color: var(--muted); }
.result-breakdown { margin: 20px 0; text-align: left; }
.result-breakdown .row {
  display: flex; justify-content: space-between; padding: 10px 0;
  border-bottom: 1px solid var(--border);
}
.result-breakdown .row:last-child { border-bottom: 0; }
.result-breakdown .row .name { color: var(--muted); }

.footer { border-top: 1px solid var(--border); padding: 28px 0; margin-top: 40px; color: var(--muted); }
.footer-inner { display: flex; flex-direction: column; gap: 4px; }
.muted { color: var(--muted); font-size: 14px; }

@media (max-width: 640px) {
  .hero h1 { font-size: 40px; }
  .topnav { display: none; }
  .question-card { padding: 20px; }
  .results-card { padding: 24px; }
}