/* ============================================================
   LearnAI — Shared Design System
   A friendly, modern, interactive AI learning playground
   ============================================================ */

:root {
  --bg: #0d1117;
  --bg-soft: #161b22;
  --bg-card: #1c2230;
  --bg-card-2: #232b3b;
  --border: #2d3748;
  --text: #e6edf3;
  --text-dim: #9aa7b8;
  --primary: #6c8cff;
  --primary-2: #8b5cf6;
  --accent: #2dd4bf;
  --accent-2: #f472b6;
  --good: #34d399;
  --bad: #f87171;
  --warn: #fbbf24;
  --radius: 16px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
  --grad: linear-gradient(135deg, #6c8cff 0%, #8b5cf6 50%, #f472b6 100%);
  --grad-soft: linear-gradient(135deg, rgba(108,140,255,0.15), rgba(139,92,246,0.12));
}

* { 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: radial-gradient(1200px 600px at 80% -10%, rgba(139,92,246,0.18), transparent 60%),
              radial-gradient(900px 500px at -10% 10%, rgba(45,212,191,0.12), transparent 55%),
              var(--bg);
  color: var(--text);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

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

.container { max-width: 1080px; margin: 0 auto; padding: 0 20px; }

/* ---------- Top nav bar ---------- */
.navbar {
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: blur(10px);
  background: rgba(13, 17, 23, 0.72);
  border-bottom: 1px solid var(--border);
}
.navbar .inner {
  max-width: 1080px; margin: 0 auto; padding: 12px 20px;
  display: flex; align-items: center; justify-content: space-between; gap: 16px;
}
.brand { font-weight: 800; font-size: 1.15rem; display: flex; align-items: center; gap: 10px; }
.brand .logo {
  width: 30px; height: 30px; border-radius: 9px; background: var(--grad);
  display: grid; place-items: center; font-size: 16px;
}
.brand span.txt { background: var(--grad); -webkit-background-clip: text; background-clip: text; color: transparent; }
.nav-links { display: flex; gap: 18px; font-size: 0.95rem; }
.nav-links a { color: var(--text-dim); }
.nav-links a:hover { color: var(--text); text-decoration: none; }

/* ---------- Hero ---------- */
.hero { text-align: center; padding: 70px 20px 40px; }
.hero h1 {
  font-size: clamp(2rem, 6vw, 3.6rem); margin: 0 0 14px; line-height: 1.1;
  background: var(--grad); -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero p { font-size: 1.15rem; color: var(--text-dim); max-width: 680px; margin: 0 auto; }
.hero .badges { margin-top: 22px; display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }
.badge {
  background: var(--grad-soft); border: 1px solid var(--border);
  padding: 6px 14px; border-radius: 999px; font-size: 0.85rem; color: var(--text);
}

/* ---------- Section headings ---------- */
.section-title { font-size: 1.6rem; margin: 40px 0 6px; }
.section-sub { color: var(--text-dim); margin: 0 0 20px; }

/* ---------- Syllabus grid (homepage) ---------- */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(290px, 1fr)); gap: 20px; }

.topic-card {
  position: relative; display: block; background: var(--bg-card);
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px; text-decoration: none; color: var(--text);
  transition: transform .18s ease, border-color .18s ease, box-shadow .18s ease;
  overflow: hidden;
}
.topic-card::before {
  content: ""; position: absolute; inset: 0; background: var(--grad-soft); opacity: 0;
  transition: opacity .18s ease;
}
.topic-card:hover { transform: translateY(-4px); border-color: var(--primary); box-shadow: var(--shadow); text-decoration: none; }
.topic-card:hover::before { opacity: 1; }
.topic-card > * { position: relative; }
.topic-card .num {
  font-size: 0.8rem; font-weight: 700; color: var(--accent); letter-spacing: 1px; text-transform: uppercase;
}
.topic-card .icon { font-size: 2.2rem; margin: 6px 0 10px; }
.topic-card h3 { margin: 0 0 8px; font-size: 1.2rem; }
.topic-card p { margin: 0; color: var(--text-dim); font-size: 0.95rem; }
.topic-card .level {
  display: inline-block; margin-top: 14px; font-size: 0.75rem; padding: 3px 10px;
  border-radius: 999px; border: 1px solid var(--border);
}
.level.beginner { color: var(--good); border-color: rgba(52,211,153,.4); }
.level.intermediate { color: var(--warn); border-color: rgba(251,191,36,.4); }
.level.advanced { color: var(--accent-2); border-color: rgba(244,114,182,.4); }

/* ---------- Topic page layout ---------- */
.page-header { padding: 50px 20px 10px; }
.page-header .eyebrow { color: var(--accent); font-weight: 700; letter-spacing: 1px; text-transform: uppercase; font-size: 0.82rem; }
.page-header h1 { font-size: clamp(1.8rem, 5vw, 2.8rem); margin: 8px 0 10px; }
.page-header p.lead { font-size: 1.15rem; color: var(--text-dim); max-width: 740px; }

.card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 26px; margin: 22px 0; box-shadow: var(--shadow);
}
.card h2 { margin-top: 0; }
.card h2 .em { font-size: 1.4em; margin-right: 8px; }

.callout {
  border-left: 4px solid var(--primary); background: var(--grad-soft);
  padding: 14px 18px; border-radius: 10px; margin: 18px 0;
}
.callout.tip { border-color: var(--accent); }
.callout.analogy { border-color: var(--accent-2); }
.callout .label { font-weight: 700; display: block; margin-bottom: 4px; }

.kbd, code {
  background: var(--bg-soft); border: 1px solid var(--border); border-radius: 6px;
  padding: 2px 7px; font-family: "SFMono-Regular", Consolas, monospace; font-size: 0.9em;
}
pre { background: var(--bg-soft); border: 1px solid var(--border); border-radius: 10px; padding: 16px; overflow:auto; }
pre code { background: none; border: none; padding: 0; }

/* ---------- Buttons / controls ---------- */
.btn {
  appearance: none; cursor: pointer; border: none; border-radius: 10px;
  padding: 11px 18px; font-size: 0.95rem; font-weight: 600; color: white;
  background: var(--grad); transition: transform .12s ease, filter .12s ease;
}
.btn:hover { filter: brightness(1.08); transform: translateY(-1px); }
.btn:active { transform: translateY(0); }
.btn.secondary { background: var(--bg-card-2); border: 1px solid var(--border); color: var(--text); }
.btn.small { padding: 7px 12px; font-size: 0.85rem; }

.controls { display: flex; flex-wrap: wrap; gap: 14px; align-items: center; margin: 16px 0; }
.control { display: flex; flex-direction: column; gap: 6px; min-width: 170px; }
.control label { font-size: 0.85rem; color: var(--text-dim); display:flex; justify-content:space-between; gap:10px;}
.control label .val { color: var(--accent); font-weight: 700; }
input[type="range"] { width: 100%; accent-color: var(--primary); }
input[type="text"], input[type="number"], select, textarea {
  background: var(--bg-soft); border: 1px solid var(--border); border-radius: 8px;
  color: var(--text); padding: 10px 12px; font-size: 0.95rem; width: 100%;
}
textarea { resize: vertical; min-height: 80px; font-family: inherit; }

canvas { max-width: 100%; border-radius: 12px; background: var(--bg-soft); border: 1px solid var(--border); }

/* ---------- Playground container ---------- */
.playground {
  background: var(--bg-card-2); border: 1px dashed var(--primary);
  border-radius: var(--radius); padding: 22px; margin: 20px 0;
}
.playground .pg-title { font-weight: 700; display: flex; align-items: center; gap: 8px; margin-bottom: 6px; }
.playground .pg-title .tag {
  font-size: 0.7rem; background: var(--primary); color: white; padding: 2px 8px; border-radius: 999px; text-transform: uppercase; letter-spacing: .5px;
}
.readout { font-family: "SFMono-Regular", Consolas, monospace; background: var(--bg-soft); border:1px solid var(--border); border-radius:10px; padding:12px 14px; }

/* ---------- Quiz ---------- */
.quiz { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 26px; margin: 24px 0; }
.quiz h2 { margin-top: 0; }
.quiz .progress-bar { height: 8px; background: var(--bg-soft); border-radius: 999px; overflow: hidden; margin: 10px 0 20px; }
.quiz .progress-bar > div { height: 100%; width: 0; background: var(--grad); transition: width .3s ease; }
.q-block { margin-bottom: 8px; }
.q-text { font-weight: 600; margin-bottom: 14px; font-size: 1.05rem; }
.q-text .qnum { color: var(--accent); margin-right: 8px; }
.options { display: flex; flex-direction: column; gap: 10px; }
.option {
  display: flex; align-items: center; gap: 12px; cursor: pointer;
  background: var(--bg-soft); border: 1px solid var(--border); border-radius: 10px;
  padding: 12px 16px; transition: border-color .15s ease, background .15s ease;
}
.option:hover { border-color: var(--primary); }
.option.selected { border-color: var(--primary); background: var(--grad-soft); }
.option.correct { border-color: var(--good); background: rgba(52,211,153,.12); }
.option.wrong { border-color: var(--bad); background: rgba(248,113,113,.12); }
.option .mark { margin-left: auto; font-weight: 700; }
.quiz-feedback { margin-top: 12px; padding: 12px 16px; border-radius: 10px; display: none; }
.quiz-feedback.show { display: block; }
.quiz-feedback.ok { background: rgba(52,211,153,.12); border: 1px solid var(--good); }
.quiz-feedback.no { background: rgba(248,113,113,.12); border: 1px solid var(--bad); }
.quiz-nav { display: flex; justify-content: space-between; align-items: center; margin-top: 20px; }
.quiz-result { text-align: center; padding: 20px 0; }
.quiz-result .score { font-size: 3rem; font-weight: 800; background: var(--grad); -webkit-background-clip: text; background-clip:text; color: transparent; }

/* ---------- Page footer nav (prev/next) ---------- */
.page-nav { display: flex; justify-content: space-between; gap: 16px; margin: 40px 0; flex-wrap: wrap; }
.page-nav a {
  flex: 1; min-width: 200px; background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px 18px; color: var(--text);
}
.page-nav a:hover { border-color: var(--primary); text-decoration: none; }
.page-nav a .dir { color: var(--text-dim); font-size: 0.8rem; }
.page-nav a.next { text-align: right; }

footer.site-footer {
  border-top: 1px solid var(--border); margin-top: 50px; padding: 30px 20px;
  text-align: center; color: var(--text-dim); font-size: 0.9rem;
}

/* ---------- Misc helpers ---------- */
.muted { color: var(--text-dim); }
.center { text-align: center; }
.row { display: flex; gap: 20px; flex-wrap: wrap; }
.row > * { flex: 1; min-width: 240px; }
.pill { display:inline-block; padding:3px 10px; border-radius:999px; border:1px solid var(--border); font-size:.8rem; }
.tag-good { color: var(--good); } .tag-bad { color: var(--bad); }
table.data { width: 100%; border-collapse: collapse; }
table.data th, table.data td { border: 1px solid var(--border); padding: 8px 12px; text-align: left; }
table.data th { background: var(--bg-soft); }

@media (max-width: 640px) {
  .nav-links { display: none; }
  .hero { padding: 40px 16px 20px; }
}