/* Cambridge Lower Secondary Mathematics 7 — Unit 1 Integers
   Self-contained stylesheet. No external fonts, no CDN. */

:root{
  --bg:#f2f5f8;
  --card:#ffffff;
  --ink:#16222e;
  --muted:#61717f;
  --line:#dbe3ea;
  --brand:#284E99;        /* Nexamind blue  */
  --brand-dk:#1D3A75;
  --brand-lt:#eaf0fa;
  --accent:#F2AA44;       /* Nexamind amber */
  --accent-lt:#fff6e6;
  --ok:#0f7a45;   --ok-bg:#e6f6ed;  --ok-line:#a8dcc0;
  --bad:#c02626;  --bad-bg:#fdecec; --bad-line:#f3bcbc;
  --purple:#4a3f8f; --purple-lt:#eeecf9;
  --radius:14px;
  --shadow:0 1px 2px rgba(16,32,48,.05), 0 6px 20px rgba(16,32,48,.06);
}

*{box-sizing:border-box}
html{scroll-behavior:smooth; scroll-padding-top:100px}
body{
  margin:0; background:var(--bg); color:var(--ink); line-height:1.6;
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  font-size:16px; -webkit-font-smoothing:antialiased;
}
.wrap{max-width:980px;margin:0 auto;padding:0 20px}
a{color:var(--brand)}
h1,h2,h3{line-height:1.25}

/* ---------------------------------------------------------------- top bar */
.topbar{background:var(--brand-dk);color:#fff;position:sticky;top:0;z-index:60;
  box-shadow:0 1px 0 rgba(0,0,0,.12)}
.topbar .wrap{display:flex;align-items:center;gap:8px;height:66px;flex-wrap:nowrap;overflow-x:auto}
.topbar a{color:#dff0f2;text-decoration:none;font-size:.9rem;font-weight:600;
  padding:6px 11px;border-radius:8px;white-space:nowrap}
.topbar a:hover{background:rgba(255,255,255,.12);color:#fff}
.topbar a.on{background:#fff;color:var(--brand-dk)}
.topbar .brand{font-weight:800;letter-spacing:.2px;color:#fff;margin-right:4px;padding-left:0}
.topbar .logo{display:flex;align-items:center;padding:4px 16px 4px 0;margin-right:10px;
  border-right:1px solid rgba(255,255,255,.25);text-decoration:none;flex:0 0 auto}
.topbar .logo:hover{background:transparent}
.topbar .logo img{height:38px;display:block;image-rendering:auto}
footer.site .by{display:flex;flex-direction:column;align-items:center;gap:10px;margin-bottom:16px}
footer.site .by img{height:56px}
footer.site .by span{font-size:.82rem;font-weight:700;letter-spacing:.12em;text-transform:uppercase;
  color:var(--brand)}
.hero .mark{display:block;height:52px;margin-bottom:18px}
@media (max-width:640px){
  .topbar .logo img{height:30px}
  footer.site .by img{height:44px}
  .hero .mark{height:40px}
}
.topbar .brand span{opacity:.65;font-weight:600}

/* ---------------------------------------------------------------- hero */
.hero{background:linear-gradient(135deg,var(--brand) 0%,var(--brand-dk) 100%);color:#fff;
  padding:44px 0 40px}
.hero h1{margin:0 0 8px;font-size:2.15rem}
.hero p{margin:0;opacity:.92;max-width:60ch}
.hero .eyebrow{text-transform:uppercase;letter-spacing:.14em;font-size:.72rem;font-weight:700;
  opacity:.8;margin-bottom:10px}
.chips{display:flex;gap:8px;flex-wrap:wrap;margin-top:18px}
.chip{background:rgba(255,255,255,.16);border:1px solid rgba(255,255,255,.25);
  padding:5px 12px;border-radius:99px;font-size:.82rem;font-weight:600}

/* ---------------------------------------------------------------- cards */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:16px;margin:22px 0}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:18px;box-shadow:var(--shadow);text-decoration:none;color:inherit;display:block;
  transition:transform .12s ease, box-shadow .12s ease, border-color .12s}
a.card:hover{transform:translateY(-2px);border-color:var(--brand);
  box-shadow:0 4px 10px rgba(14,124,138,.12),0 12px 28px rgba(16,32,48,.1)}
.card .kicker{font-size:.74rem;font-weight:800;letter-spacing:.1em;text-transform:uppercase;
  color:var(--brand);margin-bottom:6px}
.card h3{margin:0 0 6px;font-size:1.08rem}
.card p{margin:0;color:var(--muted);font-size:.92rem}
.card .meta{margin-top:12px;font-size:.8rem;color:var(--muted);display:flex;gap:12px;flex-wrap:wrap}

section.block{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  margin:22px 0;overflow:hidden;box-shadow:var(--shadow)}
section.block > h2{margin:0;padding:15px 20px;background:#eef4f6;border-bottom:1px solid var(--line);
  font-size:1.1rem;display:flex;justify-content:space-between;align-items:center;gap:12px}
section.block > h2 .tag{font-size:.74rem;font-weight:700;color:var(--muted);background:#fff;
  border:1px solid var(--line);border-radius:99px;padding:3px 11px;white-space:nowrap}
.pad{padding:18px 20px}

/* ---------------------------------------------------------------- slides */
.deck{background:#fff;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;
  box-shadow:var(--shadow);margin:22px 0;display:grid;grid-template-columns:212px minmax(0,1fr)}
.deck .rail{background:linear-gradient(180deg,var(--brand) 0%,var(--brand-dk) 100%);color:#fff;padding:14px 0;
  overflow:auto}
.deck .rail .rlbl{font-size:.66rem;font-weight:800;letter-spacing:.14em;text-transform:uppercase;
  opacity:.6;padding:0 16px 8px}
.deck .rail a{display:flex;gap:9px;align-items:flex-start;padding:9px 16px;cursor:pointer;
  font-size:.86rem;line-height:1.35;color:#dbe4f5;text-decoration:none;border-left:3px solid transparent}
.deck .rail a:hover{background:rgba(255,255,255,.09);color:#fff}
.deck .rail a.on{background:rgba(255,255,255,.16);color:#fff;border-left-color:var(--accent);
  font-weight:700}
.deck .rail a b{flex:0 0 18px;opacity:.7;font-variant-numeric:tabular-nums}
.deck .main{display:flex;flex-direction:column;min-width:0}
.deck .stage{padding:28px 32px 24px;flex:1;background:linear-gradient(180deg,#fbfdfe 0,#fff 140px)}
.deck .stage .eyebrow{font-size:.68rem;font-weight:800;letter-spacing:.14em;text-transform:uppercase;
  color:var(--brand);margin-bottom:6px}
.deck .stage h3{margin:0;font-size:1.62rem;color:var(--brand-dk);line-height:1.2}
.deck .stage .rule{height:4px;width:62px;background:var(--accent);border-radius:2px;margin:12px 0 18px}
.deck .stage ul{list-style:none;margin:0 0 18px;padding:0}
.deck .stage li{margin:0;padding:8px 0 8px 26px;position:relative;font-size:1.04rem}
.deck .stage li:before{content:"";position:absolute;left:4px;top:calc(8px + .6em);width:8px;height:8px;
  border-radius:99px;background:var(--brand)}
.deck .stage li b{color:var(--brand-dk)}
.deck .eg{background:var(--brand-lt);border:1px solid #cbe6ea;border-left:5px solid var(--brand);
  border-radius:0 12px 12px 0;padding:14px 18px}
.deck .eg .lbl{font-size:.7rem;font-weight:800;letter-spacing:.12em;text-transform:uppercase;
  color:var(--brand-dk);margin-bottom:7px}
.deck .eg div.line{font-family:"SF Mono",SFMono-Regular,Consolas,"Liberation Mono",monospace;
  font-size:1.05rem;margin:4px 0}
.deck .bar{display:flex;align-items:center;gap:12px;padding:11px 18px;background:#f5f9fa;
  border-top:1px solid var(--line)}
.deck .track{flex:1;height:6px;background:#dde6ec;border-radius:99px;overflow:hidden}
.deck .track>i{display:block;height:100%;background:var(--brand);transition:width .3s ease}
.deck .count{font-size:.84rem;color:var(--muted);font-weight:700;min-width:54px;text-align:right;
  font-variant-numeric:tabular-nums}
.deck .dots{display:none}
@media (max-width:760px){
  .deck{grid-template-columns:1fr}
  .deck .rail{display:flex;gap:4px;padding:10px;overflow-x:auto}
  .deck .rail .rlbl{display:none}
  .deck .rail a{white-space:nowrap;border-left:0;border-bottom:3px solid transparent;border-radius:8px}
  .deck .rail a.on{border-left:0;border-bottom-color:var(--accent)}
  .deck .rail a span{display:none}
}

/* teacher-deck call-out */
.teach{display:flex;gap:16px;align-items:center;flex-wrap:wrap;
  background:linear-gradient(135deg,#22315c,#151f3b);color:#eef2fa;border-radius:var(--radius);
  padding:18px 22px;margin:20px 0}
.teach .txt{flex:1;min-width:240px}
.teach h3{margin:0 0 4px;font-size:1.06rem;color:#fff}
.teach p{margin:0;font-size:.9rem;color:#aab6d2}
.teach a.btn{background:var(--accent);color:#3a2600;font-weight:800;text-decoration:none;
  padding:10px 18px;border-radius:10px;white-space:nowrap}
.teach a.btn:hover{background:#ffc069}
.teach a.alt{color:#c9d6f2;text-decoration:none;font-size:.88rem;font-weight:600}

/* ---------------------------------------------------------------- buttons */
button{font:inherit;cursor:pointer;border:1px solid transparent;border-radius:9px;
  padding:8px 15px;background:var(--brand);color:#fff;font-weight:650;transition:.13s}
button:hover{background:var(--brand-dk)}
button:active{transform:translateY(1px)}
button.ghost{background:#fff;color:var(--brand);border-color:var(--brand)}
button.ghost:hover{background:var(--brand-lt)}
button.quiet{background:#fff;color:var(--muted);border-color:var(--line)}
button.quiet:hover{background:#f4f7f9;color:var(--ink)}
button.sm{padding:5px 11px;font-size:.85rem;border-radius:8px}
.btnrow{display:flex;gap:9px;flex-wrap:wrap;align-items:center}

/* ---------------------------------------------------------------- scorebar */
.scorebar{position:sticky;top:66px;z-index:50;background:#fff;border-bottom:1px solid var(--line);
  box-shadow:0 2px 6px rgba(16,32,48,.05)}
.scorebar .wrap{display:flex;align-items:center;gap:14px;padding-top:10px;padding-bottom:10px;
  flex-wrap:wrap}
.scorebar .lbl{font-weight:750;font-size:.92rem;white-space:nowrap}
.scorebar .lbl b{color:var(--brand)}
.pbar{flex:1;min-width:120px;height:9px;background:#e6ecf1;border-radius:99px;overflow:hidden}
.pbar>i{display:block;height:100%;width:0;background:linear-gradient(90deg,var(--brand),#3aa8b5);
  transition:width .4s cubic-bezier(.2,.8,.3,1)}

/* ---------------------------------------------------------------- questions */
.qgroup{border-top:1px solid var(--line)}
.qgroup:first-child{border-top:none}
.qgroup > header{padding:14px 20px;background:#fafcfd;display:flex;justify-content:space-between;
  align-items:baseline;gap:12px;flex-wrap:wrap;cursor:pointer;user-select:none}
.qgroup > header h3{margin:0;font-size:1rem}
.qgroup > header p{margin:2px 0 0;color:var(--muted);font-size:.86rem}
.qgroup > header .res{font-size:.84rem;font-weight:700;color:var(--muted)}
.qgroup .qs{padding:2px 20px}
.qgroup.folded .qs, .qgroup.folded .gactions{display:none}

.q{display:flex;gap:13px;align-items:flex-start;padding:13px 0;border-bottom:1px dashed var(--line)}
.q:last-child{border-bottom:none}
.q .n{flex:0 0 32px;height:26px;border-radius:7px;background:var(--brand-lt);color:var(--brand-dk);
  font-weight:800;font-size:.8rem;display:flex;align-items:center;justify-content:center;margin-top:2px}
.q .body{flex:1;min-width:0}
.q .prompt{margin:0 0 8px}
.q .prompt .math{font-family:"SF Mono",SFMono-Regular,Consolas,"Liberation Mono",monospace;
  font-size:1.08rem;font-weight:600}
.q .marks{font-size:.75rem;color:var(--muted);font-weight:700;margin-left:6px}
.defn{display:block;color:var(--muted);font-size:.9rem;margin-top:4px}
.wordbox{display:block;margin-top:8px;background:#f1f4f7;border:1px solid var(--line);
  border-radius:9px;padding:8px 12px;font-size:.88rem;font-weight:600;color:var(--brand-dk)}

input[type=text]{font:inherit;padding:7px 11px;border:1.6px solid var(--line);border-radius:9px;
  width:180px;max-width:100%;background:#fbfcfe}
input[type=text]:focus{outline:none;border-color:var(--brand);background:#fff;
  box-shadow:0 0 0 3px rgba(14,124,138,.12)}
.opts{display:flex;flex-direction:column;gap:7px;margin:2px 0 4px}
.opts label{display:flex;align-items:flex-start;gap:9px;background:#fbfcfe;border:1.6px solid var(--line);
  border-radius:9px;padding:7px 12px;cursor:pointer;font-size:.95rem}
.opts label:hover{border-color:var(--brand);background:#fff}
.opts input{margin-top:4px}
.inline{display:flex;gap:9px;align-items:center;flex-wrap:wrap}

.fb{margin-top:9px;font-size:.9rem;border-radius:9px;padding:9px 12px;display:none;
  border:1px solid transparent}
.fb.show{display:block}
.fb.ok{background:var(--ok-bg);color:var(--ok);border-color:var(--ok-line)}
.fb.bad{background:var(--bad-bg);color:var(--bad);border-color:var(--bad-line)}
.fb.rev{background:var(--accent-lt);color:#7a4d00;border-color:#f0d9a8}
.fb b{font-weight:800}
.gactions{padding:12px 20px 18px;background:#fafcfd;border-top:1px solid var(--line);
  display:flex;gap:9px;flex-wrap:wrap;align-items:center}

/* ---------------------------------------------------------------- summary */
.summary{list-style:none;margin:0;padding:0}
.summary li{padding:10px 0 10px 30px;border-bottom:1px solid var(--line);position:relative}
.summary li:last-child{border-bottom:none}
.summary li:before{content:"";position:absolute;left:6px;top:19px;width:8px;height:8px;
  border-radius:99px;background:var(--accent)}
.keywords{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:12px}
.kw{background:#fbfcfe;border:1px solid var(--line);border-left:4px solid var(--brand);
  border-radius:0 10px 10px 0;padding:11px 14px}
.kw b{display:block;color:var(--brand-dk)}
.kw span{font-size:.9rem;color:var(--muted)}
.kw em{display:block;font-size:.85rem;color:var(--brand-dk);margin-top:5px}

/* ---------------------------------------------------------------- videos */
.vid{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  overflow:hidden;box-shadow:var(--shadow)}
.vid .frame{position:relative;padding-top:56.25%;background:#0d1720}
.vid .frame iframe{position:absolute;inset:0;width:100%;height:100%;border:0}
.vid .info{padding:13px 15px}
.vid .info h4{margin:0 0 4px;font-size:.98rem}
.vid .info p{margin:0;color:var(--muted);font-size:.86rem}
.badge{display:inline-block;font-size:.7rem;font-weight:800;letter-spacing:.06em;
  text-transform:uppercase;padding:2px 8px;border-radius:99px;margin-right:6px}
.badge.uk{background:#e6ecf9;color:#284E99}
.badge.us{background:#fdf0dd;color:#8a5a0d}
.badge.ext{background:var(--purple-lt);color:var(--purple)}
.offline-note{background:var(--accent-lt);border:1px solid #f0d9a8;color:#7a4d00;
  border-radius:10px;padding:11px 14px;font-size:.9rem;margin:14px 0}

/* ---------------------------------------------------------------- tables */
table.tbl{width:100%;border-collapse:collapse;font-size:.93rem}
table.tbl th,table.tbl td{border:1px solid var(--line);padding:9px 11px;text-align:left;
  vertical-align:top}
table.tbl th{background:#eef4f6;font-weight:750}
table.tbl tr:nth-child(even) td{background:#fbfcfd}

/* ---------------------------------------------------------------- downloads */
.dl{display:flex;align-items:center;gap:12px;padding:12px 14px;border:1px solid var(--line);
  border-radius:11px;background:#fff;text-decoration:none;color:inherit;transition:.12s}
.dl:hover{border-color:var(--brand);background:var(--brand-lt)}
.dl .ic{flex:0 0 38px;height:38px;border-radius:9px;background:#fdeaea;color:#c02626;
  display:flex;align-items:center;justify-content:center;font-weight:800;font-size:.72rem}
.dl b{display:block;font-size:.95rem}
.dl span{font-size:.82rem;color:var(--muted)}

footer.site{color:var(--muted);font-size:.85rem;padding:34px 0 60px;text-align:center}
footer.site a{color:var(--muted)}

.notice{background:var(--purple-lt);border:1px solid #d7d0f0;color:#3f3475;border-radius:11px;
  padding:12px 15px;font-size:.9rem}

@media (max-width:640px){
  .hero h1{font-size:1.65rem}
  .deck .stage{padding:22px 20px;min-height:300px}
  .q .n{flex-basis:26px}
  .scorebar{top:66px}
}
@media print{
  .topbar,.scorebar,.gactions,.deck .bar,button,.offline-note{display:none !important}
  body{background:#fff}
  section.block,.card,.deck{box-shadow:none;break-inside:avoid}
}

/* ---------------------------------------------------- geometry figures (u5) */
.figwrap{display:block;margin:10px 0 2px}
.figwrap svg.fig{max-width:100%;height:auto;background:#fbfcfe;border:1px solid var(--line);
  border-radius:12px;padding:6px}
@media print{.figwrap svg.fig{border-color:#ccc;background:#fff}}

/* ------------------------------------------------------- language switcher */
.topbar .langbar{margin-left:auto;display:inline-flex;gap:2px;align-items:center;
  background:rgba(255,255,255,.12);border-radius:8px;padding:2px}
.topbar .langbar a,.topbar .langbar b{font-size:.74rem;font-weight:800;letter-spacing:.04em;
  padding:4px 8px;border-radius:6px;line-height:1;text-decoration:none}
.topbar .langbar a{color:rgba(255,255,255,.72)}
.topbar .langbar a:hover{background:rgba(255,255,255,.16);color:#fff}
.topbar .langbar b{background:var(--accent);color:#26313f}
.figbox{margin:10px 0 2px}
.figbox svg.fig{max-width:100%;height:auto;background:#fbfcfe;border:1px solid var(--line);
  border-radius:12px;padding:6px}
.gloss{display:block;color:var(--muted);font-size:.86rem;font-style:italic;margin-top:2px}
@media print{.topbar .langbar{display:none}.figbox svg.fig{border-color:#ccc;background:#fff}}

/* --------------------------------------------------------- data tables (u6) */
.dtabwrap{margin:10px 0 2px}
.dtab{border-collapse:collapse;font-size:.92rem;background:#fff}
.dtab th,.dtab td{border:1px solid var(--line);padding:5px 11px;text-align:left}
.dtab thead th{background:var(--brand-lt);color:var(--brand-dk);font-weight:700}
.dtab tr.tot td{font-weight:700;background:#f6f8fb}
.dtabwrap figcaption{font-size:.84rem;color:var(--muted);margin-top:5px}

/* --------------------------------------------------------------- fractions */
.frac{display:inline-flex;flex-direction:column;vertical-align:-0.45em;
  line-height:1.05;text-align:center;margin:0 1px}
.frac sup,.frac sub{font-size:.72em;position:static;padding:0 3px}
.frac sup{border-bottom:1.4px solid currentColor}