/* ═══════════════════════════════════════════════
   MARKETING PLATFORM — Mobile-First Design
   ═══════════════════════════════════════════════ */
:root {
  --bg:      #0d1117;  --bg2: #161b22;  --bg3: #21262d;  --card: #1c2129;
  --border:  #30363d;
  --primary: #7c6dfa;  --primary-dim: rgba(124,109,250,.12);
  --green:   #22c55e;  --green-dim:  rgba(34,197,94,.12);
  --red:     #ef4444;  --red-dim:    rgba(239,68,68,.1);
  --yellow:  #f59e0b;  --blue: #38bdf8;  --orange: #fb923c;  --pink: #ec4899;
  --text:    #e6edf3;  --text2: #8b949e;  --text3: #484f58;
  --radius:  16px;     --r2: 12px;  --r3: 8px;
  --shadow:  0 4px 24px rgba(0,0,0,.4);
  --ch6:#7c6dfa; --ch7:#06b6d4; --ch8:#10b981; --ch9:#f59e0b;
  --ch10:#ef4444; --ch11:#8b5cf6; --ch12:#ec4899; --ch13:#14b8a6; --ch14:#84cc16;
  --safe-b: env(safe-area-inset-bottom, 0px);
  --nav-h: 72px;
}
[data-theme="light"] {
  --bg:#f0f4f8; --bg2:#ffffff; --bg3:#e8edf2; --card:#ffffff;
  --border:#d1d9e0; --text:#1a1f2e; --text2:#52606d; --text3:#9aa5b4;
  --shadow:0 4px 20px rgba(0,0,0,.08);
}
*, *::before, *::after { box-sizing:border-box; margin:0; padding:0; }
html { -webkit-text-size-adjust:100%; scroll-behavior:smooth; }
body {
  background:var(--bg); color:var(--text);
  font-family:-apple-system,'SF Pro Display','Segoe UI',system-ui,sans-serif;
  min-height:100vh; line-height:1.6; overflow-x:hidden;
  -webkit-font-smoothing:antialiased;
}
button { font-family:inherit; }

/* ── HEADER ── */
.app-header {
  position:sticky; top:0; z-index:100;
  background:var(--bg2); border-bottom:1px solid var(--border);
  padding:0 16px; height:52px;
  display:flex; align-items:center; gap:10px;
}
.hdr-logo { font-size:17px; font-weight:800; letter-spacing:-.3px;
  background:linear-gradient(135deg,var(--primary),var(--blue));
  -webkit-background-clip:text; -webkit-text-fill-color:transparent; }
.hdr-spacer { flex:1; }
.hdr-pill { background:var(--bg3); border:1px solid var(--border);
  border-radius:20px; padding:4px 12px; font-size:12px; color:var(--text2);
  white-space:nowrap; }
.hdr-pill strong { color:var(--primary); }
.hdr-btn { background:var(--bg3); border:1px solid var(--border);
  border-radius:8px; min-width:36px; height:36px; display:flex;
  align-items:center; justify-content:center; cursor:pointer;
  font-size:16px; flex-shrink:0; -webkit-tap-highlight-color:transparent; }

/* ── VIEWS ── */
.view { display:none; }
.view.active { display:block; animation:fadeUp .22s ease; }
@keyframes fadeUp { from{opacity:0;transform:translateY(10px)} to{opacity:1;transform:none} }

/* ══════════════════════════════════════
   HOME VIEW
   ══════════════════════════════════════ */
.home-wrap { max-width:680px; margin:0 auto; padding:20px 16px 100px; }
.home-hero { text-align:center; padding:24px 0 20px; }
.home-hero h1 { font-size:24px; font-weight:800; letter-spacing:-.4px; margin-bottom:6px; }
.home-hero p { color:var(--text2); font-size:14px; }

/* Overall stats row */
.stats-row { display:grid; grid-template-columns:1fr 1fr; gap:10px; margin-bottom:20px; }
.stat-card { background:var(--card); border:1px solid var(--border); border-radius:var(--r2);
  padding:14px; text-align:center; }
.stat-card .sn { font-size:26px; font-weight:800; color:var(--primary); }
.stat-card .sl { font-size:11px; color:var(--text3); margin-top:2px; text-transform:uppercase; letter-spacing:.04em; }

/* Random mode button */
.random-btn {
  width:100%; padding:16px; margin-bottom:20px;
  background:linear-gradient(135deg,var(--primary),#5b52e8);
  border:none; border-radius:var(--radius); cursor:pointer;
  display:flex; align-items:center; justify-content:center; gap:10px;
  color:#fff; font-size:16px; font-weight:700; letter-spacing:-.2px;
  box-shadow:0 4px 20px rgba(124,109,250,.35);
  -webkit-tap-highlight-color:transparent; transition:transform .15s,opacity .15s;
}
.random-btn:active { transform:scale(.97); opacity:.9; }
.random-btn .rb-icon { font-size:22px; }
.random-btn .rb-sub { font-size:12px; opacity:.8; font-weight:500; margin-top:1px; }

/* Chapter grid */
.section-label { font-size:12px; font-weight:700; color:var(--text3); text-transform:uppercase;
  letter-spacing:.06em; margin-bottom:10px; }
.ch-grid { display:grid; grid-template-columns:1fr 1fr; gap:10px; }
@media(min-width:500px){ .ch-grid { grid-template-columns:repeat(3,1fr); } }
@media(min-width:700px){ .ch-grid { grid-template-columns:repeat(3,1fr); } }

.ch-card {
  background:var(--card); border:1px solid var(--border); border-radius:var(--radius);
  padding:16px 14px; cursor:pointer; position:relative; overflow:hidden;
  border-top:3px solid var(--clr);
  -webkit-tap-highlight-color:transparent; transition:transform .15s,box-shadow .15s;
}
.ch-card:active { transform:scale(.96); }
.ch-card .ce { font-size:24px; margin-bottom:6px; display:block; }
.ch-card .ct { font-size:11px; font-weight:700; color:var(--clr); margin-bottom:3px; }
.ch-card .cs { font-size:12px; font-weight:600; color:var(--text); line-height:1.35; margin-bottom:8px; }
.ch-pbar { height:3px; background:var(--bg3); border-radius:2px; }
.ch-pfill { height:100%; border-radius:2px; background:var(--clr); transition:.4s; }
.ch-meta { font-size:11px; color:var(--text3); margin-top:6px; }
.ch-done .ct::after { content:' ✓'; color:var(--green); }

/* Exam card in grid */
.exam-card-home {
  grid-column:1/-1;
  background:var(--primary-dim); border:1px solid rgba(124,109,250,.25);
  border-radius:var(--radius); padding:16px; cursor:pointer;
  display:flex; align-items:center; gap:14px;
  -webkit-tap-highlight-color:transparent; transition:transform .15s;
}
.exam-card-home:active { transform:scale(.97); }
.exam-card-home.locked { opacity:.45; cursor:default; }
.ec-ico { font-size:32px; flex-shrink:0; }
.ec-info .ec-t { font-size:15px; font-weight:700; color:var(--primary); }
.ec-info .ec-s { font-size:12px; color:var(--text3); margin-top:2px; }
.ec-arr { margin-left:auto; font-size:20px; color:var(--primary); flex-shrink:0; }

/* ══════════════════════════════════════
   QUESTION VIEW
   ══════════════════════════════════════ */
.q-wrap { max-width:680px; margin:0 auto; padding:12px 16px calc(var(--nav-h) + var(--safe-b) + 12px); }

/* Top mini bar */
.q-topbar {
  display:flex; align-items:center; gap:8px; margin-bottom:14px;
  font-size:13px; color:var(--text2);
}
.q-topbar .back-lnk { background:var(--bg3); border:1px solid var(--border);
  border-radius:8px; padding:6px 10px; cursor:pointer; color:var(--text2);
  font-size:13px; white-space:nowrap; -webkit-tap-highlight-color:transparent; }
.q-topbar .back-lnk:active { opacity:.7; }
.q-mode-badge { border:1px solid var(--border); border-radius:20px; padding:3px 10px;
  font-size:11px; font-weight:700; white-space:nowrap; }
.q-topbar-spacer { flex:1; }
.q-frac { font-size:13px; font-weight:700; color:var(--text2); }

/* Progress ring / bar */
.q-progress { height:4px; background:var(--bg3); border-radius:2px; margin-bottom:18px; overflow:hidden; }
.q-progress-fill { height:100%; border-radius:2px; transition:.35s; }

/* Question card */
.q-card { background:var(--card); border:1px solid var(--border);
  border-radius:var(--radius); padding:20px 18px 18px; margin-bottom:14px; }
.q-num { font-size:11px; font-weight:700; color:var(--text3); text-transform:uppercase;
  letter-spacing:.05em; margin-bottom:10px;
  display:flex; align-items:center; gap:6px; flex-wrap:wrap; }
.diff-pip { width:6px; height:6px; border-radius:50%; flex-shrink:0; }
.diff-pip.diff-easy, .diff-easy .diff-pip { background:var(--green); }
.diff-pip.diff-medium, .diff-medium .diff-pip { background:var(--yellow); }
.diff-pip.diff-hard, .diff-hard .diff-pip { background:var(--red); }
.q-text { font-size:16px; font-weight:600; line-height:1.55; color:var(--text); }
@media(min-width:500px){ .q-text { font-size:17px; } }

/* Options */
.options { display:flex; flex-direction:column; gap:9px; }
.opt {
  background:var(--bg3); border:1.5px solid var(--border);
  border-radius:var(--r2); padding:14px 14px; cursor:pointer;
  display:flex; gap:12px; align-items:flex-start; min-height:52px;
  transition:border-color .15s, background .15s; position:relative;
  -webkit-tap-highlight-color:transparent;
}
.opt:not(.locked):active { transform:scale(.98); }
.opt-letter {
  width:28px; height:28px; border-radius:7px; background:var(--bg2);
  border:1px solid var(--border); display:flex; align-items:center; justify-content:center;
  font-weight:800; font-size:13px; flex-shrink:0; margin-top:1px;
}
.opt-text { font-size:14px; line-height:1.5; flex:1; padding-top:3px; }
.opt:not(.locked):hover { border-color:var(--primary); background:var(--primary-dim); }
.opt.correct { border-color:var(--green); background:var(--green-dim); }
.opt.correct .opt-letter { background:rgba(34,197,94,.2); border-color:var(--green); color:var(--green); }
.opt.wrong { border-color:var(--red); background:var(--red-dim); }
.opt.wrong .opt-letter { background:rgba(239,68,68,.15); border-color:var(--red); color:var(--red); }
.opt.dimmed { opacity:.38; }
.opt.locked { cursor:default; }

/* ── EXPLANATION ACCORDION ── */
.explain-section { margin-bottom:10px; }
.explain-section:empty { display:none; }
.acc-item {
  background:var(--card); border:1px solid var(--border);
  border-radius:var(--r2); overflow:hidden; margin-bottom:8px;
}
.acc-head {
  display:flex; align-items:center; gap:10px; padding:13px 14px;
  cursor:pointer; -webkit-tap-highlight-color:transparent; user-select:none;
}
.acc-head:active { background:var(--bg3); }
.acc-icon { font-size:18px; flex-shrink:0; }
.acc-label { font-size:14px; font-weight:600; flex:1; }
.acc-arr { font-size:18px; color:var(--text3); transition:transform .2s; flex-shrink:0; }
.acc-item.open .acc-arr { transform:rotate(90deg); }
.acc-body { display:none; padding:0 14px 14px; border-top:1px solid var(--border); }
.acc-item.open .acc-body { display:block; animation:fadeUp .18s ease; }
.acc-body p, .acc-body li { font-size:14px; color:var(--text2); line-height:1.65; }
.acc-body ul { padding-left:18px; }
.acc-body ul li { margin-bottom:4px; }
.acc-body .pt { margin-top:10px; }

/* Correct box inside accordion */
.ans-correct-line {
  display:flex; align-items:flex-start; gap:10px; padding:11px 12px;
  background:var(--green-dim); border:1px solid rgba(34,197,94,.25);
  border-radius:var(--r3); margin-bottom:10px;
}
.ans-correct-line .aletter { background:rgba(34,197,94,.2); border:1px solid rgba(34,197,94,.4);
  border-radius:6px; padding:2px 8px; font-weight:800; font-size:13px; color:var(--green);
  flex-shrink:0; }
.ans-correct-line p { font-size:14px; color:var(--text); font-weight:600; flex:1; }

/* Wrong items */
.wrong-pill {
  display:flex; gap:8px; padding:9px 12px; border-radius:var(--r3);
  background:var(--red-dim); border:1px solid rgba(239,68,68,.15);
  margin-bottom:7px; font-size:13px; color:var(--text2); align-items:flex-start;
}
.wrong-pill .wl { color:var(--red); font-weight:700; flex-shrink:0; font-size:13px; }

/* Memory, example boxes */
.tip-row { display:flex; gap:8px; align-items:flex-start; padding:10px 12px;
  border-radius:var(--r3); margin-bottom:7px; font-size:13px; }
.tip-yellow { background:rgba(245,158,11,.08); border:1px solid rgba(245,158,11,.2); color:var(--text2); }
.tip-blue { background:rgba(56,189,248,.06); border:1px solid rgba(56,189,248,.15); color:var(--text2); }
.tip-orange { background:rgba(251,146,60,.07); border:1px solid rgba(251,146,60,.18); color:var(--text2); }
.tip-row .te { font-size:18px; flex-shrink:0; }

/* Keywords */
.kw-pills { display:flex; flex-wrap:wrap; gap:6px; margin-top:10px; }
.kpill { background:var(--primary-dim); border:1px solid rgba(124,109,250,.22);
  color:var(--primary); border-radius:20px; padding:3px 10px; font-size:12px; font-weight:600; }

/* ── BOTTOM NAV BAR ── */
.bottom-nav {
  position:fixed; bottom:0; left:0; right:0; z-index:200;
  background:var(--bg2); border-top:1px solid var(--border);
  padding:10px 16px calc(10px + var(--safe-b));
  display:flex; align-items:center; gap:8px;
}
.bnav-prev, .bnav-next {
  border:none; border-radius:var(--r2); cursor:pointer;
  display:flex; align-items:center; gap:6px; font-weight:700;
  font-size:14px; padding:0 14px; height:48px;
  -webkit-tap-highlight-color:transparent; transition:opacity .15s, transform .15s;
  flex-shrink:0;
}
.bnav-prev:active,.bnav-next:active { transform:scale(.95); }
.bnav-prev { background:var(--bg3); border:1px solid var(--border); color:var(--text2); min-width:52px; }
.bnav-prev:disabled { opacity:.3; cursor:default; }
.bnav-counter { flex:1; text-align:center; font-size:14px; font-weight:700; color:var(--text2); }
.bnav-next { background:var(--bg3); border:1px solid var(--border); color:var(--text2);
  min-width:52px; flex-shrink:0; }
.bnav-next.active-next {
  background:var(--primary); color:#fff; border-color:transparent;
  box-shadow:0 4px 16px rgba(124,109,250,.4); flex:1;
  justify-content:center; font-size:15px;
}
.bnav-next.finish { background:var(--green); box-shadow:0 4px 16px rgba(34,197,94,.35); }

/* ── RESULT AFTER ANSWER ── */
.answer-result-bar {
  display:flex; align-items:center; gap:10px; padding:12px 14px;
  border-radius:var(--r2); margin-bottom:10px; font-size:14px; font-weight:600;
}
.answer-result-bar.correct-bar { background:var(--green-dim); border:1px solid rgba(34,197,94,.3); color:var(--green); }
.answer-result-bar.wrong-bar { background:var(--red-dim); border:1px solid rgba(239,68,68,.25); color:var(--red); }

/* ══════════════════════════════════════
   SUMMARY VIEW
   ══════════════════════════════════════ */
.sum-wrap { max-width:680px; margin:0 auto; padding:20px 16px 100px; }
.sum-hero { text-align:center; padding:24px 0 20px; }
.sum-emoji { font-size:52px; margin-bottom:10px; }
.sum-title { font-size:22px; font-weight:800; margin-bottom:6px; }
.sum-sub { color:var(--text2); font-size:14px; }
.sum-stats { display:grid; grid-template-columns:repeat(2,1fr); gap:10px; margin:20px 0; }
.sum-stat { background:var(--card); border:1px solid var(--border); border-radius:var(--r2);
  padding:14px; text-align:center; }
.sum-stat .sn { font-size:24px; font-weight:800; color:var(--primary2,var(--primary)); }
.sum-stat .sl { font-size:11px; color:var(--text3); margin-top:2px; }
.sum-section { margin-bottom:16px; }
.sum-section h3 { font-size:13px; font-weight:700; color:var(--text3); text-transform:uppercase;
  letter-spacing:.05em; margin-bottom:10px; }
.sum-concept { background:var(--card); border:1px solid var(--border); border-radius:var(--r3);
  padding:10px 14px; margin-bottom:7px; font-size:14px; display:flex; gap:8px; }
.sum-concept .scn { color:var(--primary); font-weight:700; flex-shrink:0; }
.sum-trick { background:rgba(245,158,11,.07); border:1px solid rgba(245,158,11,.18);
  border-radius:var(--r3); padding:10px 14px; margin-bottom:7px;
  font-size:13px; color:var(--text2); display:flex; gap:8px; }
.sum-cta { display:flex; flex-direction:column; gap:8px; margin-top:20px; }
.sum-btn { padding:14px; border-radius:var(--r2); border:none; cursor:pointer;
  font-size:15px; font-weight:700; text-align:center;
  -webkit-tap-highlight-color:transparent; transition:transform .15s; }
.sum-btn:active { transform:scale(.97); }
.sum-btn-primary { background:var(--primary); color:#fff; box-shadow:0 4px 16px rgba(124,109,250,.3); }
.sum-btn-secondary { background:var(--bg3); border:1px solid var(--border); color:var(--text); }
.sum-btn-green { background:var(--green); color:#fff; }

/* ══════════════════════════════════════
   EXAM VIEW
   ══════════════════════════════════════ */
.exam-wrap { max-width:680px; margin:0 auto; padding:16px 16px 120px; }
.exam-hdr { text-align:center; margin-bottom:20px; }
.exam-hdr h2 { font-size:20px; font-weight:800; margin-bottom:8px; }
.exam-timer { font-size:28px; font-weight:800; font-family:monospace; color:var(--yellow);
  background:var(--bg3); border:1px solid var(--border); border-radius:var(--r2);
  padding:6px 20px; display:inline-block; }
.exam-timer.danger { color:var(--red); animation:pulse .8s ease infinite; }
@keyframes pulse { 0%,100%{opacity:1} 50%{opacity:.6} }
.exam-q-card { background:var(--card); border:1px solid var(--border);
  border-radius:var(--radius); padding:18px; margin-bottom:10px; }
.exam-q-top { display:flex; gap:6px; margin-bottom:10px; flex-wrap:wrap; }
.exam-q-text { font-size:15px; font-weight:600; line-height:1.55; margin-bottom:12px; }
.exam-opts { display:flex; flex-direction:column; gap:7px; }
.exam-opt { background:var(--bg3); border:1.5px solid var(--border);
  border-radius:var(--r3); padding:11px 13px; cursor:pointer;
  display:flex; gap:10px; align-items:flex-start; min-height:46px; font-size:13px;
  -webkit-tap-highlight-color:transparent; transition:.15s; }
.exam-opt:active { transform:scale(.98); }
.exam-opt.sel { border-color:var(--primary); background:var(--primary-dim); }
.exam-opt.sel .opt-letter { background:var(--primary); color:#fff; border-color:var(--primary); }
.exam-opt.ev-correct { border-color:var(--green); background:var(--green-dim); }
.exam-opt.ev-wrong { border-color:var(--red); background:var(--red-dim); }
.exam-submit-bar { position:fixed; bottom:0; left:0; right:0; background:var(--bg2);
  border-top:1px solid var(--border); padding:12px 16px calc(12px + var(--safe-b)); }
.exam-submit { width:100%; padding:14px; background:var(--primary); color:#fff;
  border:none; border-radius:var(--r2); font-size:16px; font-weight:700; cursor:pointer; }

/* ══════════════════════════════════════
   RESULTS VIEW
   ══════════════════════════════════════ */
.res-wrap { max-width:680px; margin:0 auto; padding:20px 16px 100px; }
.score-ring { width:130px; height:130px; margin:0 auto 16px; position:relative; }
.score-ring svg { width:100%; height:100%; transform:rotate(-90deg); }
.score-ring .ring-bg { fill:none; stroke:var(--bg3); stroke-width:8; }
.score-ring .ring-fill { fill:none; stroke-width:8; stroke-linecap:round;
  transition:stroke-dashoffset .8s cubic-bezier(.4,0,.2,1); }
.score-center { position:absolute; top:50%; left:50%; transform:translate(-50%,-50%);
  text-align:center; }
.score-pct { font-size:26px; font-weight:800; }
.score-lbl { font-size:11px; color:var(--text3); }
.res-title { text-align:center; font-size:20px; font-weight:800; margin-bottom:4px; }
.res-sub { text-align:center; color:var(--text2); font-size:14px; margin-bottom:20px; }
.ch-res { display:flex; flex-direction:column; gap:8px; margin-bottom:16px; }
.ch-ri { background:var(--card); border:1px solid var(--border); border-radius:var(--r2);
  padding:12px 14px; display:flex; align-items:center; gap:10px; }
.ch-ri-ico { font-size:20px; flex-shrink:0; }
.ch-ri-name { flex:1; font-size:13px; font-weight:600; min-width:0; }
.ch-ri-bar { width:60px; height:5px; background:var(--bg3); border-radius:3px; overflow:hidden; flex-shrink:0; }
.ch-ri-fill { height:100%; border-radius:3px; }
.ch-ri-pct { font-size:13px; font-weight:700; min-width:36px; text-align:right; flex-shrink:0; }
.res-actions { display:flex; flex-direction:column; gap:8px; }
.res-btn { padding:13px; border-radius:var(--r2); border:none; cursor:pointer;
  font-size:15px; font-weight:700; -webkit-tap-highlight-color:transparent; }

/* ══════════════════════════════════════
   TERM POPUP
   ══════════════════════════════════════ */
.term-popup { position:fixed; z-index:400; max-width:300px; width:calc(100vw - 32px);
  background:var(--card); border:1px solid var(--border); border-radius:var(--radius);
  padding:16px; box-shadow:0 8px 32px rgba(0,0,0,.5); display:none; }
.term-popup.show { display:block; animation:fadeUp .15s ease; }
.term-popup-head { display:flex; justify-content:space-between; align-items:center; margin-bottom:8px; }
.term-popup-head h4 { font-size:15px; font-weight:700; color:var(--primary); }
.term-close { font-size:22px; color:var(--text3); cursor:pointer; line-height:1; padding:0 4px; }
.term-popup p { font-size:13px; color:var(--text2); margin-bottom:4px; line-height:1.55; }
.term-popup .en { font-size:11px; color:var(--text3); font-style:italic; }
.kterm { border-bottom:1px dashed var(--primary); color:var(--primary); cursor:pointer;
  display:inline; -webkit-tap-highlight-color:transparent; }

/* ══════════════════════════════════════
   MISC UTILITIES
   ══════════════════════════════════════ */
::-webkit-scrollbar { width:4px; }
::-webkit-scrollbar-track { background:var(--bg); }
::-webkit-scrollbar-thumb { background:var(--bg3); border-radius:2px; }
@media(max-width:360px) {
  .ch-grid { grid-template-columns:1fr 1fr; }
  .q-text { font-size:15px; }
}