/* ===== TCS IPA Prep — styles ===== */
:root {
  --bg: #0f1420; --bg2: #161d2e; --card: #1b2437; --card2:#222c42;
  --line: #2a3550; --text: #e7ecf6; --muted: #97a3bd; --muted2:#6b7796;
  --accent: #5b8cff; --accent2:#7c6cff; --good:#34d399; --bad:#f87171;
  --warn:#fbbf24; --chip:#24304a;
  --shadow: 0 8px 30px rgba(0,0,0,.35);
  --radius: 14px;
}
:root[data-theme="light"] {
  --bg:#f4f6fb; --bg2:#eef1f8; --card:#ffffff; --card2:#f7f9fd;
  --line:#e2e7f0; --text:#1a2233; --muted:#5b6579; --muted2:#8a93a6;
  --accent:#3563e9; --accent2:#6d5cff; --good:#0ea472; --bad:#dc4b4b;
  --warn:#d99413; --chip:#eef2fb;
  --shadow:0 8px 30px rgba(30,50,90,.10);
}
* { box-sizing: border-box; }
html,body { margin:0; padding:0; }
body {
  background: radial-gradient(1200px 600px at 80% -10%, rgba(124,108,255,.10), transparent 60%), var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Inter, system-ui, sans-serif;
  line-height: 1.55; min-height:100vh;
}
a { color: var(--accent); }
h1,h2,h3 { line-height:1.2; margin:.2em 0 .5em; }
code, pre, .mono { font-family: "JetBrains Mono", "Fira Code", Consolas, monospace; }

/* topbar */
.topbar {
  position: sticky; top:0; z-index:50; display:flex; align-items:center; gap:18px;
  padding: 12px 22px; background: rgba(15,20,32,.72); backdrop-filter: blur(12px);
  border-bottom:1px solid var(--line);
}
:root[data-theme="light"] .topbar { background: rgba(255,255,255,.75); }
.brand { font-weight:800; font-size:1.15rem; cursor:pointer; letter-spacing:.3px; white-space:nowrap; }
.brand .logo { color:var(--accent); }
.brand-sub { color:var(--muted); font-weight:600; font-size:.9rem; }
.nav { display:flex; gap:4px; flex:1; flex-wrap:wrap; }
.nav a { padding:8px 14px; border-radius:10px; color:var(--muted); text-decoration:none; font-weight:600; font-size:.92rem; }
.nav a:hover { color:var(--text); background:var(--card); }
.nav a.active { color:#fff; background:linear-gradient(135deg,var(--accent),var(--accent2)); }
:root[data-theme="light"] .nav a.active { color:#fff; }
.theme-btn { background:var(--card); color:var(--text); border:1px solid var(--line); border-radius:10px; width:38px; height:38px; cursor:pointer; font-size:1.1rem; }
.profile-btn { display:inline-flex; align-items:center; gap:6px; background:var(--card); color:var(--text); border:1px solid var(--line); border-radius:10px; padding:8px 12px; cursor:pointer; font-weight:700; font-size:.88rem; white-space:nowrap; }
.profile-btn:hover { border-color:var(--accent); }

/* modal */
#modal .modal-overlay { position:fixed; inset:0; z-index:100; background:rgba(0,0,0,.55); backdrop-filter:blur(4px); display:flex; align-items:center; justify-content:center; padding:20px; }
#modal .modal { width:100%; max-width:440px; }
#modal { display:none; }
#modal.show { display:block; }
@media(max-width:560px){ .profile-btn span{max-width:80px;overflow:hidden;text-overflow:ellipsis;} }

.app { max-width: 1080px; margin: 26px auto 60px; padding: 0 20px; }
.foot { text-align:center; color:var(--muted2); font-size:.82rem; padding:24px; border-top:1px solid var(--line); }

/* cards & layout */
.card { background:var(--card); border:1px solid var(--line); border-radius:var(--radius); padding:20px; box-shadow:var(--shadow); }
.grid { display:grid; gap:16px; }
.grid.cols-2 { grid-template-columns:repeat(2,1fr); }
.grid.cols-3 { grid-template-columns:repeat(3,1fr); }
.grid.cols-4 { grid-template-columns:repeat(4,1fr); }
@media(max-width:820px){ .grid.cols-2,.grid.cols-3,.grid.cols-4{grid-template-columns:1fr 1fr;} }
@media(max-width:520px){ .grid.cols-2,.grid.cols-3,.grid.cols-4{grid-template-columns:1fr;} .nav a{padding:7px 10px;font-size:.85rem;} }
.row { display:flex; gap:12px; align-items:center; flex-wrap:wrap; }
.spread { justify-content:space-between; }
.muted { color:var(--muted); }
.small { font-size:.85rem; }
.center { text-align:center; }

/* hero */
.hero { background:linear-gradient(135deg, rgba(91,140,255,.16), rgba(124,108,255,.12)); border:1px solid var(--line);
  border-radius:18px; padding:26px 26px; margin-bottom:22px; }
.hero h1 { font-size:1.9rem; margin:0 0 6px; }
.hero p { color:var(--muted); margin:0; max-width:60ch; }

/* buttons */
.btn { display:inline-flex; align-items:center; gap:8px; cursor:pointer; border:none; border-radius:11px;
  padding:11px 18px; font-weight:700; font-size:.95rem; font-family:inherit;
  background:var(--card2); color:var(--text); border:1px solid var(--line); transition:.15s; text-decoration:none; }
.btn:hover { transform:translateY(-1px); border-color:var(--accent); }
.btn.primary { background:linear-gradient(135deg,var(--accent),var(--accent2)); color:#fff; border:none; }
.btn.ghost { background:transparent; }
.btn.sm { padding:7px 12px; font-size:.85rem; border-radius:9px; }
.btn:disabled { opacity:.5; cursor:not-allowed; transform:none; }

/* chips / badges */
.chip { display:inline-block; padding:3px 10px; border-radius:999px; background:var(--chip); color:var(--muted);
  font-size:.74rem; font-weight:700; letter-spacing:.3px; }
.chip.prob { color:var(--warn); }
.chip.good { color:var(--good); } .chip.bad { color:var(--bad); }
.badge-dot { display:inline-block;width:8px;height:8px;border-radius:50%;background:var(--accent); margin-right:6px; }

/* section tiles */
.sec-tile { display:flex; flex-direction:column; gap:6px; cursor:pointer; text-decoration:none; color:inherit; }
.sec-tile .n { font-size:1.8rem; font-weight:800; }
.sec-tile .lbl { color:var(--muted); font-weight:700; font-size:.9rem; text-transform:uppercase; letter-spacing:.5px; }
.sec-tile:hover { border-color:var(--accent); }
.bar { height:8px; background:var(--bg2); border-radius:99px; overflow:hidden; }
.bar > span { display:block; height:100%; background:linear-gradient(90deg,var(--accent),var(--accent2)); }

/* stat */
.stat { text-align:center; }
.stat .v { font-size:2rem; font-weight:800; }
.stat .k { color:var(--muted); font-size:.82rem; text-transform:uppercase; letter-spacing:.5px; }

/* question card */
.qwrap { max-width:760px; margin:0 auto; }
.qhead { display:flex; justify-content:space-between; align-items:center; margin-bottom:8px; }
.qtext { font-size:1.12rem; font-weight:600; margin:10px 0 4px; }
.qcode { background:var(--bg2); border:1px solid var(--line); border-radius:10px; padding:12px 14px; margin:12px 0;
  white-space:pre; overflow-x:auto; font-size:.86rem; color:var(--text); }
.opts { display:flex; flex-direction:column; gap:10px; margin-top:14px; }
.opt { display:flex; gap:12px; align-items:center; padding:13px 15px; border:1.5px solid var(--line); border-radius:11px;
  cursor:pointer; background:var(--card2); transition:.12s; }
.opt:hover { border-color:var(--accent); }
.opt .k { width:26px;height:26px;flex:none;border-radius:7px;background:var(--bg2);display:grid;place-items:center;font-weight:700;font-size:.8rem; }
.opt.correct { border-color:var(--good); background:rgba(52,211,153,.12); }
.opt.wrong { border-color:var(--bad); background:rgba(248,113,113,.12); }
.opt.disabled { cursor:default; }
.explain { margin-top:14px; padding:12px 15px; border-radius:10px; background:var(--bg2); border-left:3px solid var(--accent); font-size:.92rem; }

/* mock */
.timer { font-variant-numeric:tabular-nums; font-weight:800; font-size:1.1rem; padding:6px 14px; border-radius:10px; background:var(--card2); border:1px solid var(--line); }
.timer.danger { color:var(--bad); border-color:var(--bad); }
.qnav { display:flex; flex-wrap:wrap; gap:6px; }
.qnav button { width:34px;height:34px;border-radius:8px;border:1px solid var(--line);background:var(--card2);color:var(--muted);cursor:pointer;font-weight:700;font-size:.8rem; }
.qnav button.answered { background:var(--accent); color:#fff; border:none; }
.qnav button.current { outline:2px solid var(--accent); }
.qnav button.flag { border-color:var(--warn); color:var(--warn); }

/* progress ring / result */
.result-score { font-size:3rem; font-weight:800; background:linear-gradient(135deg,var(--accent),var(--accent2)); -webkit-background-clip:text; background-clip:text; -webkit-text-fill-color:transparent; }
table.tbl { width:100%; border-collapse:collapse; }
table.tbl th, table.tbl td { text-align:left; padding:10px 12px; border-bottom:1px solid var(--line); }
table.tbl th { color:var(--muted); font-size:.8rem; text-transform:uppercase; letter-spacing:.5px; }

/* learn */
.tabs { display:flex; gap:6px; flex-wrap:wrap; margin-bottom:18px; }
.tabs button { padding:9px 15px; border-radius:10px; border:1px solid var(--line); background:var(--card); color:var(--muted); cursor:pointer; font-weight:700; font-size:.9rem; }
.tabs button.active { background:linear-gradient(135deg,var(--accent),var(--accent2)); color:#fff; border:none; }
.lesson h2 { border-bottom:1px solid var(--line); padding-bottom:8px; }
.lesson pre { background:var(--bg2); border:1px solid var(--line); border-radius:10px; padding:14px; overflow-x:auto; font-size:.84rem; }
.lesson code { background:var(--chip); padding:1px 6px; border-radius:5px; font-size:.88em; }
.lesson table { width:100%; border-collapse:collapse; margin:12px 0; }
.lesson td, .lesson th { border:1px solid var(--line); padding:8px 10px; text-align:left; font-size:.9rem; }
details.acc { border:1px solid var(--line); border-radius:11px; margin-bottom:10px; background:var(--card); overflow:hidden; }
details.acc > summary { cursor:pointer; padding:14px 16px; font-weight:700; list-style:none; display:flex; justify-content:space-between; align-items:center; }
details.acc > summary::-webkit-details-marker { display:none; }
details.acc[open] > summary { border-bottom:1px solid var(--line); }
.acc-body { padding:16px; }

/* filter bar */
.filterbar { display:flex; gap:10px; flex-wrap:wrap; align-items:center; margin-bottom:16px; }
select, input[type=text] { background:var(--card2); color:var(--text); border:1px solid var(--line); border-radius:9px; padding:8px 12px; font-family:inherit; font-size:.9rem; }

.empty { text-align:center; color:var(--muted); padding:40px; }
.kbd { background:var(--chip); border:1px solid var(--line); border-radius:6px; padding:1px 7px; font-size:.8rem; font-family:monospace; }
.hl-good{color:var(--good);font-weight:700;} .hl-bad{color:var(--bad);font-weight:700;} .hl-warn{color:var(--warn);font-weight:700;}
.divider{height:1px;background:var(--line);margin:18px 0;}

/* ============ MOBILE / RESPONSIVE ============ */
html, body { overflow-x: hidden; max-width: 100%; }
.qwrap, .card, .hero, .qcode, pre, .lesson pre { max-width: 100%; }
img, table { max-width: 100%; }
* { min-width: 0; }

@media (max-width: 760px) {
  .app { padding: 0 13px; margin: 16px auto 40px; }
  /* topbar: brand left, profile+theme right, nav on its own scrollable row */
  .topbar { flex-wrap: wrap; gap: 8px; padding: 10px 13px; }
  .brand { order: 0; margin-right: auto; font-size: 1.05rem; }
  .profile-btn { order: 1; padding: 7px 10px; }
  .theme-btn { order: 2; width: 36px; height: 36px; }
  .nav { order: 3; flex: 0 0 100%; width: 100%; flex-wrap: nowrap; overflow-x: auto;
         gap: 6px; padding-bottom: 2px; scrollbar-width: none; -webkit-overflow-scrolling: touch; }
  .nav::-webkit-scrollbar { display: none; }
  .nav a { flex: 0 0 auto; white-space: nowrap; padding: 8px 13px; }
  .pf-name { max-width: 90px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
             display: inline-block; vertical-align: bottom; }

  .hero { padding: 20px 17px; margin-bottom: 18px; }
  .hero h1 { font-size: 1.45rem; }
  .hero p { font-size: .92rem; }
  h1 { font-size: 1.5rem; }
  h3 { font-size: 1.05rem; }

  .grid.cols-2, .grid.cols-3 { grid-template-columns: 1fr; }
  .grid.cols-4 { grid-template-columns: 1fr 1fr; }
  .grid { gap: 12px; }

  .card { padding: 15px; }
  .qtext { font-size: 1.02rem; }
  .opt { padding: 12px 13px; }
  .opt .k { width: 24px; height: 24px; }
  .qcode, .lesson pre { font-size: .76rem; padding: 10px 12px; }
  .lesson code { font-size: .82em; word-break: break-word; }

  table.tbl th, table.tbl td { padding: 8px 7px; font-size: .84rem; }
  .tbl .bar { width: 64px !important; }
  .lesson td, .lesson th { padding: 6px 8px; font-size: .82rem; }
  .lesson table { display: block; overflow-x: auto; }

  .result-score { font-size: 2.4rem; }
  .tabs button { font-size: .82rem; padding: 8px 11px; }
  .filterbar select, .filterbar input { flex: 1 1 auto; }
}

@media (max-width: 420px) {
  .hero h1 { font-size: 1.3rem; }
  .stat .v { font-size: 1.5rem; }
  .stat .k { font-size: .72rem; }
  .nav a { padding: 7px 11px; font-size: .85rem; }
  .btn { padding: 10px 14px; font-size: .9rem; }
  .qnav button { width: 30px; height: 30px; font-size: .74rem; }
}