/* Study With Me — chapter page v3 (interactive lessons + question bank). Loaded after style.css, only by v3 pages. */
body.v3 { --max: 1080px; --science-ink: #0f766e; background: var(--bg); }
.v3 :focus-visible { outline: 3px solid #f59e0b; outline-offset: 2px; border-radius: 6px; }
.skip { position: absolute; left: -999px; top: 0; background: #fff; color: #000; padding: .5rem 1rem; z-index: 99; }
.skip:focus { left: .5rem; top: .5rem; }
.sr { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.muted { color: var(--muted); }

/* header progress */
.v3h { padding: .6rem 0 .5rem; }
.v3h .logo-badge { width: 34px; height: 34px; }
.hprog { display: flex; align-items: center; gap: .5rem; margin-top: .45rem; font-size: .75rem; }
.hprog .bar { flex: 1; height: 8px; border-radius: 99px; background: rgba(255,255,255,.25); overflow: hidden; max-width: 420px; }
.hprog .bar i { display: block; height: 100%; width: 0; background: linear-gradient(90deg, #fde68a, #34d399); border-radius: 99px; transition: width .4s; }
.hp-l, .hp-t, .hp-q { white-space: nowrap; opacity: .95; }
.hp-q { margin-left: auto; }

/* hero */
.chero { padding: .4rem 0 .6rem; }
.kicker { margin: 0 0 .25rem; font-size: .78rem; color: var(--science-ink); font-weight: 600; }
.chero .chapter-title { font-size: clamp(1.45rem, 5vw, 2.1rem); margin-bottom: 0; }
.ten { margin: .1rem 0 .7rem; color: var(--muted); font-weight: 600; }
.chips { display: flex; flex-wrap: wrap; gap: .4rem; }
.stats .pill { background: #fff; border: 1px solid var(--border); color: var(--ink); }
.howto { margin-top: .8rem; background: #fff; border: 1px solid var(--border); border-radius: 14px; padding: .7rem .9rem; font-size: .9rem; }
.howto ol { margin: .2rem 0; padding-left: 1.2rem; }
.howto p { margin: .2rem 0; }

/* generic buttons */
.btn { display: inline-flex; align-items: center; gap: .35rem; border: 0; border-radius: 999px; padding: .55rem 1rem; font-weight: 700; font-size: .9rem;
  background: var(--science); color: #fff; min-height: 40px; }
.btn:hover { filter: brightness(1.07); }
.btn.sm { padding: .4rem .8rem; font-size: .82rem; min-height: 36px; }
.btn.ghost { background: #fff; color: var(--science-ink); border: 1.5px solid #99d5cf; }
.btn.ok { background: var(--ok); } .btn.bad { background: #b45309; }
.btn[disabled] { opacity: .5; cursor: default; }
.lact { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: .8rem; }

/* video */
.yt { position: relative; margin: 0 auto .4rem; }
.yt.v { aspect-ratio: 9 / 16; max-width: 300px; }
.yt.h { aspect-ratio: 16 / 9; }
.ytf, .yt iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; border-radius: 14px; }
.ytf { padding: 0; overflow: hidden; background: linear-gradient(160deg, #1e3a8a, #0d9488); color: #fff; cursor: pointer; }
.ytf img { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; }
.ytp { position: absolute; left: 50%; top: 50%; width: 68px; height: 48px; margin: -24px 0 0 -34px; background: #e11d48; border-radius: 14px; box-shadow: 0 6px 20px rgba(0,0,0,.35); }
.ytp::after { content: ""; position: absolute; left: 27px; top: 14px; border-style: solid; border-width: 10px 0 10px 17px; border-color: transparent transparent transparent #fff; }
.ytt { position: absolute; left: 0; right: 0; bottom: 0; padding: 1.6rem .7rem .6rem; font-size: .8rem; font-weight: 600; text-align: left;
  background: linear-gradient(transparent, rgba(0,0,0,.75)); line-height: 1.35; }
.ytl { display: block; text-align: center; font-size: .75rem; color: var(--muted); margin-top: .3rem; text-decoration: underline; }
.vcard .plgrid { display: grid; gap: 1rem; margin-top: 1rem; }
.plc h3 { font-size: .95rem; margin: 0 0 .4rem; }
.long-soon, .short-soon { display: flex; gap: .7rem; align-items: flex-start; background: #eff6ff; border: 1px dashed #93c5fd; border-radius: 14px; padding: .8rem .9rem; font-size: .9rem; color: #1e3a8a; }
.long-soon .ico, .short-soon .ico { font-size: 1.6rem; line-height: 1; }
.long-soon details { margin-top: .5rem; } .long-soon summary { cursor: pointer; font-weight: 600; }
.vid { width: 100%; border-radius: 10px; background: #000; aspect-ratio: 16/9; }
.vlab { font-size: .82rem; font-weight: 600; margin: .6rem 0 .2rem; }
.short { background: #0f172a; border-radius: 18px; padding: .7rem; color: #e2e8f0; }
.short .sh-h { font-weight: 700; font-size: .85rem; margin: 0 0 .5rem; } .short .sh-h small { opacity: .7; font-weight: 400; }
.short .chips { margin-top: .5rem; justify-content: center; }
.short .chip { background: #1e293b; color: #e2e8f0; border-color: #334155; }
.short .chip.on { background: #0d9488; border-color: #0d9488; color: #fff; }
.short .ytl { color: #94a3b8; }
.soon-note { font-size: .72rem; opacity: .75; margin: .4rem 0 0; text-align: center; }

/* pdf list */
.pdfs { list-style: none; margin: 0; padding: 0; }
.pdfs li { display: flex; align-items: center; gap: .7rem; padding: .7rem 0; border-bottom: 1px solid var(--border); flex-wrap: wrap; }
.pdfs li:last-child { border-bottom: 0; }
.pdf-i { font-size: 1.5rem; } .pdf-t { flex: 1; min-width: 200px; } .pdf-t small { display: block; color: var(--muted); font-size: .78rem; }
.pdf-a { display: flex; gap: .4rem; }

/* toc */
.toc ol { list-style: none; margin: 0; padding: 0; display: grid; gap: .35rem; }
.toc li a { display: flex; align-items: center; gap: .6rem; padding: .45rem .6rem; border-radius: 10px; background: #faf7f2; border: 1px solid var(--border); }
.toc li a:hover { background: var(--science-soft); }
.tn { width: 1.7rem; height: 1.7rem; flex-shrink: 0; border-radius: 8px; display: grid; place-items: center; font-weight: 700; font-size: .78rem; background: #fff; border: 1px solid var(--border); }
.tt { flex: 1; font-size: .9rem; font-weight: 600; }
.mdot, .mlegend i { width: 12px; height: 12px; border-radius: 50%; background: #e5e7eb; flex-shrink: 0; display: inline-block; }
.mdot[data-s="1"], .mlegend .d1 { background: #fbbf24; }
.mdot[data-s="2"], .mlegend .d2 { background: #34d399; }
.mdot[data-s="3"], .mlegend .d3 { background: #0d9488; box-shadow: 0 0 0 3px #99f6e4; }
.mlegend { font-size: .72rem; font-weight: 400; color: var(--muted); display: inline-flex; gap: .3rem; align-items: center; margin-left: auto; flex-wrap: wrap; }
.mlegend i { width: 9px; height: 9px; margin-left: .35rem; }
.card h2 small { font-weight: 400; }

/* lesson */
.lesson { background: #fff; border: 1px solid var(--border); border-radius: 20px; box-shadow: var(--shadow); padding: 1rem 1.05rem 1.1rem; margin: 0 0 1.2rem; scroll-margin-top: calc(var(--hh, 100px) + 10px); }
.lh { display: flex; gap: .7rem; align-items: flex-start; margin-bottom: .6rem; }
.ln { width: 2.3rem; height: 2.3rem; flex-shrink: 0; border-radius: 12px; display: grid; place-items: center; font-weight: 700; color: #fff; background: linear-gradient(135deg, #1e3a8a, #0d9488); }
.lt { flex: 1; min-width: 0; } .lt h2 { margin: 0; font-size: 1.2rem; line-height: 1.35; } .le { margin: .1rem 0 0; color: var(--muted); font-size: .8rem; }
.mbadge { font-size: .72rem; font-weight: 700; padding: .25rem .55rem; border-radius: 99px; background: #f3f4f6; color: #6b7280; white-space: nowrap; }
.mbadge[data-s="1"] { background: #fef3c7; color: #92400e; } .mbadge[data-s="2"] { background: #dcfce7; color: #166534; } .mbadge[data-s="3"] { background: #0d9488; color: #fff; }
.lgrid { display: grid; gap: 1rem; }
.lmain > p { margin: .45rem 0; }
.lmain ul, .lmain ol { margin: .4rem 0; padding-left: 1.25rem; } .lmain li { margin: .2rem 0; }
mark { background: #fef08a; padding: 0 .15em; border-radius: 3px; color: inherit; }
.eq { font-family: "Noto Sans Devanagari", system-ui, sans-serif; background: #f0fdfa; border: 1px solid #99f6e4; border-radius: 8px; padding: .12rem .45rem; display: inline-block; margin: .1rem 0;
  font-size: .95em; line-height: 1.9; white-space: normal; }
.eq.skel { background: #fff7ed; border-color: #fdba74; }
.eq.w { background: #f5f3ff; border-color: #c4b5fd; }
.eqb { margin: .5rem 0; overflow-x: auto; } .eqb .eq { font-size: 1.02rem; padding: .35rem .7rem; }
.eq sub, .f sub, .bal sub { font-size: .72em; line-height: 0; } .eq sup, .f sup { font-size: .7em; line-height: 0; }
.st { font-size: .78em; color: #475569; }
.arr { margin: 0 .3em; font-weight: 700; color: #0f766e; }
.arr.c { display: inline-flex; flex-direction: column; align-items: center; vertical-align: middle; line-height: 1; margin: 0 .4em; }
.arr.c .ct, .arr.c .cb { font-size: .62em; font-weight: 600; color: #b45309; white-space: nowrap; }
.arr.c .ca { font-size: 1.15em; letter-spacing: .3em; }
.worked { margin: .8rem 0; border: 1.5px solid #bfdbfe; background: #f8fbff; border-radius: 14px; padding: .7rem .9rem; }
.worked .wh { font-weight: 700; color: #1e40af; margin-bottom: .3rem; font-size: .92rem; }
.worked p { margin: .35rem 0; }
.remember { background: var(--accent-soft); border-left: 4px solid var(--accent); border-radius: 0 12px 12px 0; padding: .55rem .8rem; margin: .6rem 0; font-size: .92rem; }
.remember > b { color: #92400e; display: block; font-size: .78rem; text-transform: uppercase; letter-spacing: .03em; }
.remember p { margin: .2rem 0; }
.keyp { margin-top: .8rem; background: linear-gradient(135deg, #ecfeff, #f0fdf4); border: 1px solid #a7f3d0; border-radius: 14px; padding: .6rem .9rem; font-size: .9rem; }
.keyp ul { margin: .3rem 0 0; padding-left: 1.15rem; }
.tbl { overflow-x: auto; margin: .6rem 0; }
.tbl table { border-collapse: collapse; width: 100%; font-size: .88rem; background: #fff; }
.tbl th, .tbl td { border: 1px solid var(--border); padding: .4rem .55rem; text-align: left; vertical-align: top; }
.tbl th { background: #f0fdfa; color: #134e4a; }
.fig { margin: .8rem 0; } .fig img { border-radius: 12px; display: block; width: 100%; height: auto; background: #f8fafc; }
.fig figcaption, .fig + figcaption { font-size: .78rem; color: var(--muted); margin-top: .3rem; text-align: center; }
.fig.svg svg { width: 100%; height: auto; display: block; }
.fig.imgs { display: grid; gap: .6rem; grid-template-columns: 1fr 1fr; }
.fig.imgs figure { margin: 0; } .fig.imgs.n3 { grid-template-columns: 1fr 1fr 1fr; }
.fig.cards { display: grid; gap: .5rem; grid-template-columns: 1fr; }
.ic { display: flex; gap: .6rem; align-items: flex-start; background: #fafaf9; border: 1px solid var(--border); border-radius: 12px; padding: .55rem .7rem; font-size: .88rem; }
.ic-i { font-size: 1.4rem; line-height: 1.2; }
.lcheck { margin-top: 1rem; border-top: 2px dashed var(--border); padding-top: .8rem; }
.lcheck h3 { margin: 0 0 .6rem; font-size: 1.02rem; } .lcheck h3 small { color: var(--muted); font-weight: 400; }

/* questions */
.q { border: 1.5px solid var(--border); border-radius: 14px; padding: .75rem .85rem; margin-bottom: .75rem; background: #fff; transition: border-color .15s, background .15s; }
.q.ok { border-color: #86efac; background: #f6fef9; } .q.bad { border-color: #fca5a5; background: #fffafa; } .q.done-w { border-color: #c4b5fd; }
.qh { display: flex; gap: .55rem; align-items: flex-start; flex-wrap: wrap; margin-bottom: .55rem; }
.qn { width: 1.75rem; height: 1.75rem; flex-shrink: 0; border-radius: 8px; display: grid; place-items: center; font-size: .75rem; font-weight: 700; background: var(--science); color: #fff; }
.qs { flex: 1; min-width: 60%; font-weight: 600; font-size: .95rem; } .qs p { margin: .1rem 0 .3rem; }
.qmeta { display: flex; gap: .3rem; flex-wrap: wrap; width: 100%; padding-left: 2.3rem; margin-top: -.15rem; }
.qtag, .qmarks, .prev { font-size: .66rem; font-weight: 700; padding: .12rem .45rem; border-radius: 6px; white-space: nowrap; }
.t-board { background: #fee2e2; color: #991b1b; } .t-model { background: #fef3c7; color: #92400e; } .t-ncert { background: #e0e7ff; color: #3730a3; } .t-prac { background: #f1f5f9; color: #475569; }
.qmarks { background: #ecfeff; color: #155e75; } .prev { background: #f5f5f4; color: #57534e; }
.opts { display: grid; gap: .4rem; } .opts.tf { grid-template-columns: 1fr 1fr; }
.opt { display: flex; gap: .55rem; align-items: flex-start; width: 100%; text-align: left; border: 1.5px solid var(--border); background: #fafafa; border-radius: 11px;
  padding: .55rem .7rem; font-size: .92rem; min-height: 44px; color: var(--ink); }
.opt:hover:not(:disabled) { border-color: var(--science); background: var(--science-soft); }
.opt:disabled { cursor: default; }
.ol { width: 1.45rem; height: 1.45rem; flex-shrink: 0; border-radius: 7px; background: #e7e5e4; display: grid; place-items: center; font-size: .75rem; font-weight: 700; }
.opt.right { border-color: var(--ok); background: var(--ok-soft); font-weight: 600; } .opt.right .ol { background: var(--ok); color: #fff; }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); } .opt.wrong .ol { background: var(--bad); color: #fff; }
.opt.tried { opacity: .6; text-decoration: line-through; }
.fb { margin-top: .55rem; font-size: .88rem; padding: .45rem .65rem; border-radius: 9px; font-weight: 600; }
.fb.ok { background: var(--ok-soft); color: #166534; } .fb.bad { background: var(--bad-soft); color: #991b1b; } .fb.info { background: #eff6ff; color: #1e40af; }
.hint { margin-top: .5rem; background: #fffbeb; border: 1px solid #fde68a; border-radius: 9px; padding: .45rem .65rem; font-size: .87rem; }
.hint p { display: inline; margin: 0; }
.ex { margin-top: .5rem; background: #f8fafc; border-left: 4px solid #0d9488; border-radius: 0 9px 9px 0; padding: .5rem .7rem; font-size: .88rem; }
.ex p { margin: .2rem 0; } .ex > b { color: #0f766e; }
.blank { display: inline-block; min-width: 4.5em; border-bottom: 2px solid #94a3b8; color: transparent; }
.fillrow { display: flex; gap: .4rem; flex-wrap: wrap; align-items: center; }
.fillin, .wans, .msel, .bin { font: inherit; font-size: 16px; border: 1.5px solid #cbd5e1; border-radius: 10px; padding: .45rem .6rem; background: #fff; color: var(--ink); }
.fillin { flex: 1; min-width: 180px; } .fillin.ok { border-color: var(--ok); background: var(--ok-soft); } .fillin.bad { border-color: var(--bad); }
.wans { width: 100%; resize: vertical; }
.wbtns { margin-top: .45rem; }
.model { margin-top: .6rem; background: #f5f3ff; border: 1px solid #ddd6fe; border-radius: 12px; padding: .6rem .8rem; font-size: .9rem; }
.model .mh { font-weight: 700; color: #5b21b6; font-size: .82rem; margin-bottom: .2rem; }
.model p { margin: .3rem 0; } .model ul, .model ol { margin: .3rem 0; padding-left: 1.2rem; }
.selfmark { display: flex; gap: .4rem; flex-wrap: wrap; align-items: center; margin-top: .5rem; font-size: .85rem; }
.match .mright { font-size: .85rem; background: #f8fafc; border-radius: 10px; padding: .45rem .6rem; margin-bottom: .5rem; display: flex; flex-wrap: wrap; gap: .25rem .8rem; }
.mrow { display: grid; grid-template-columns: 1fr auto 1.6rem; gap: .5rem; align-items: center; padding: .35rem 0; border-bottom: 1px dashed var(--border); }
.msel { max-width: 46vw; min-height: 40px; } .msel.ok { border-color: var(--ok); background: var(--ok-soft); } .msel.bad { border-color: var(--bad); background: var(--bad-soft); }
.mres { font-weight: 700; } .match + .btn { margin-top: .6rem; }
.bal { display: flex; flex-wrap: wrap; align-items: center; gap: .35rem; font-size: 1.05rem; padding: .4rem 0; }
.bterm { display: inline-flex; align-items: center; gap: .2rem; background: #f0fdfa; border: 1px solid #99f6e4; border-radius: 10px; padding: .2rem .4rem .2rem .25rem; }
.bin { width: 3.1rem; text-align: center; padding: .3rem .2rem; } .bin.ok { border-color: var(--ok); } .bin.bad { border-color: var(--bad); }
.plus { font-weight: 700; color: #64748b; }
.tally { font-size: .8rem; margin: .3rem 0 .5rem; display: flex; flex-wrap: wrap; gap: .3rem; }
.tally span { border-radius: 7px; padding: .15rem .45rem; background: #fee2e2; color: #991b1b; font-weight: 600; } .tally span.eqok { background: #dcfce7; color: #166534; }
.crow { margin: .35rem 0 .55rem; } .crow .ct { display: block; font-size: .78rem; color: var(--muted); font-weight: 600; margin-bottom: .25rem; }
.chip { border: 1.5px solid var(--border); background: #fff; border-radius: 999px; padding: .35rem .75rem; font-size: .82rem; font-weight: 600; min-height: 36px; color: var(--ink); }
.chip[aria-checked="true"] { border-color: #0d9488; background: #ccfbf1; }
.chip.right { border-color: var(--ok) !important; background: var(--ok-soft) !important; } .chip.wrong { border-color: var(--bad) !important; background: var(--bad-soft) !important; }

/* bank */
.bank > h2 { margin-bottom: .4rem; }
.bintro { font-size: .9rem; color: #374151; } .bintro p { margin: .3rem 0; }
.bnav { position: sticky; top: var(--hh, 92px); z-index: 5; background: rgba(255,255,255,.96); padding: .5rem 0; margin: .4rem 0 .8rem; border-bottom: 1px solid var(--border); overflow-x: auto; flex-wrap: nowrap; }
.bnav .chip { white-space: nowrap; } .bnav .chip small { color: var(--muted); font-weight: 400; }
.bsec { scroll-margin-top: calc(var(--hh, 100px) + 60px); margin-bottom: 1.4rem; }
.bh { display: flex; align-items: center; gap: .6rem; border-bottom: 2px solid #ccfbf1; margin: 1rem 0 .7rem; padding-bottom: .35rem; }
.bh h3 { margin: 0; font-size: 1.05rem; flex: 1; }
.sscore { font-size: .75rem; font-weight: 700; background: #f0fdfa; color: #0f766e; padding: .2rem .55rem; border-radius: 99px; white-space: nowrap; }
.review .rvbox { margin-top: .8rem; } .rv-empty { background: #f0fdf4; border: 1px solid #bbf7d0; border-radius: 12px; padding: .7rem .9rem; }
.sheet td:first-child { width: 34%; font-weight: 600; }
.pager { gap: .5rem; } .pager a { background: #fff; border: 1px solid var(--border); padding: .45rem .9rem; border-radius: 99px; font-weight: 600; }

@media (min-width: 700px) {
  .vcard .plgrid { grid-template-columns: 1fr 1fr; }
  .toc ol { grid-template-columns: 1fr 1fr; }
  .fig.cards { grid-template-columns: 1fr 1fr; }
  .lesson { padding: 1.3rem 1.5rem 1.4rem; }
}
@media (min-width: 940px) {
  .lgrid { grid-template-columns: minmax(0, 1fr) 290px; align-items: start; }
  .lside { position: sticky; top: calc(var(--hh, 100px) + 12px); }
  .toc ol { grid-template-columns: 1fr 1fr 1fr; }
  .opts:not(.tf) { grid-template-columns: 1fr 1fr; }
  .q[data-t="ar"] .opts { grid-template-columns: 1fr; }
}
@media (max-width: 420px) {
  .hp-l { display: none; }
  .fig.imgs.n3 { grid-template-columns: 1fr 1fr; }
  .mrow { grid-template-columns: 1fr; } .msel { max-width: 100%; width: 100%; } .mres { display: none; }
  .qmeta { padding-left: 0; }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; scroll-behavior: auto !important; } }
/* monetisation-ready bits (chapter pages) */
.hcta { display: flex; flex-wrap: wrap; gap: .5rem; align-items: center; margin-top: .8rem; }
.shsub { display: block; margin-top: .5rem; font-size: .8rem; font-weight: 700; color: #b00000; text-decoration: none; text-align: center; }
.shsub:hover { text-decoration: underline; }
.srcnote { font-size: .78rem; color: var(--muted); text-align: center; margin: 1rem 0 .5rem; }
.lesson + .subcta, .lesson + .adslot { margin-top: 1.25rem; }
.premium .btn[disabled] { background: #9ca3af; }
.btn.ytbtn { background: #cc0000; color: #fff; } .btn.ytbtn:hover { background: #b00000; }
.short .shsub { color: #fecaca; }