:root {
  --ink: #12182b;
  --muted: #5a6378;
  --line: #e3e6ee;
  --bg: #fbfaf7;
  --card: #ffffff;
  --navy: #14224f;
  --navy-2: #1d2f6b;
  --saffron: #f2a516;
  --saffron-dark: #b97800;
  --good: #14804a;
  --good-bg: #e6f5ec;
  --bad: #b3261e;
  --bad-bg: #fcebe9;
  --warn-bg: #fff4d9;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(18, 24, 43, .06), 0 6px 20px rgba(18, 24, 43, .06);
}
@media (prefers-color-scheme: dark) {
  :root {
    --ink: #eef0f7; --muted: #a2a9bf; --line: #2a3350; --bg: #0d1226; --card: #151c36;
    --navy: #0a1030; --navy-2: #26397f; --good-bg: #12301f; --bad-bg: #371714; --warn-bg: #3a2f10;
    --shadow: 0 1px 2px rgba(0,0,0,.4);
  }
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; font: 16px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; color: var(--ink); background: var(--bg); }
h1, h2, h3 { font-family: Georgia, "Times New Roman", serif; line-height: 1.2; margin: 0 0 .5em; }
h1 { font-size: clamp(2rem, 5vw, 3.1rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2rem); }
a { color: var(--navy-2); }
@media (prefers-color-scheme: dark) { a { color: #9db4ff; } }
.wrap { max-width: 1080px; margin: 0 auto; padding: 0 20px; }
.btn { display: inline-block; border: 0; cursor: pointer; border-radius: 999px; padding: .7em 1.4em; font: inherit; font-weight: 600; text-decoration: none; background: var(--saffron); color: #1a1200; }
.btn:hover { filter: brightness(.95); }
.btn.secondary { background: transparent; color: inherit; border: 1.5px solid var(--line); }
.btn.dark { background: var(--navy); color: #fff; }
.btn[disabled] { opacity: .45; cursor: not-allowed; }
.btn.small { padding: .4em .9em; font-size: .9rem; }

/* header */
.site-header { background: var(--navy); color: #fff; position: sticky; top: 0; z-index: 10; }
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; padding-top: 12px; padding-bottom: 12px; flex-wrap: wrap; }
.brand { font-family: Georgia, serif; font-weight: 700; font-size: 1.2rem; color: #fff; text-decoration: none; }
.brand span { color: var(--saffron); }
.nav { display: flex; gap: 4px; flex-wrap: wrap; }
.nav a { color: #cdd5f2; text-decoration: none; padding: .4em .8em; border-radius: 999px; font-size: .95rem; }
.nav a:hover, .nav a.active { background: rgba(255,255,255,.14); color: #fff; }

/* landing */
.hero { background: linear-gradient(160deg, var(--navy), var(--navy-2)); color: #fff; padding: 72px 0 80px; }
.hero p.lead { font-size: 1.2rem; max-width: 640px; color: #d6dcf5; }
.hero .cta { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 24px; }
.hero .btn.secondary { color: #fff; border-color: rgba(255,255,255,.4); }
section.block { padding: 64px 0; }
section.alt { background: var(--card); border-block: 1px solid var(--line); }
.grid { display: grid; gap: 18px; }
.grid.cols-2 { grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }
.grid.cols-4 { grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); }
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px; box-shadow: var(--shadow); }
.card h3 { font-size: 1.1rem; font-family: system-ui, sans-serif; font-weight: 700; }
.step-num { display: inline-grid; place-items: center; width: 32px; height: 32px; border-radius: 50%; background: var(--saffron); color: #1a1200; font-weight: 700; margin-bottom: 10px; }
.stats { display: flex; gap: 28px; flex-wrap: wrap; margin-top: 8px; }
.stat b { display: block; font-size: 2rem; font-family: Georgia, serif; }
.stat span { color: var(--muted); font-size: .9rem; }
.price-card { display: flex; flex-direction: column; }
.price-card.featured { border: 2px solid var(--saffron); position: relative; }
.price-card .tag { position: absolute; top: -12px; right: 16px; background: var(--saffron); color: #1a1200; font-size: .75rem; font-weight: 700; padding: 2px 10px; border-radius: 999px; }
.price { font-family: Georgia, serif; font-size: 2.2rem; font-weight: 700; margin: 4px 0; }
.price small { font: 400 .9rem system-ui; color: var(--muted); display: block; }
.hero .stat span { color: #c3cbee; }
.price-card ul { padding-left: 1.1em; color: var(--muted); flex: 1; margin: 12px 0 16px; }
.price-card li { margin-bottom: 4px; }
.soon { font-size: .75rem; background: var(--warn-bg); padding: 1px 8px; border-radius: 999px; }
details { border-bottom: 1px solid var(--line); padding: 14px 0; }
summary { cursor: pointer; font-weight: 600; }
footer.site-footer { padding: 36px 0; color: var(--muted); font-size: .9rem; border-top: 1px solid var(--line); }

/* app */
main.app { max-width: 860px; margin: 0 auto; padding: 28px 20px 80px; }
.muted { color: var(--muted); }
.row { display: flex; gap: 12px; flex-wrap: wrap; align-items: center; }
.row.between { justify-content: space-between; }
label.field { display: grid; gap: 4px; font-weight: 600; font-size: .9rem; min-width: 180px; flex: 1; }
select, input[type="search"] { font: inherit; padding: .55em .7em; border: 1.5px solid var(--line); border-radius: 10px; background: var(--card); color: var(--ink); }
.chip { display: inline-block; font-size: .8rem; padding: 2px 10px; border-radius: 999px; background: var(--warn-bg); color: var(--ink); }
.chip.phy { background: #e3ecff; } .chip.che { background: #e6f5ec; } .chip.bio { background: #fde9f0; }
@media (prefers-color-scheme: dark) { .chip.phy { background: #1c2a55; } .chip.che { background: #12301f; } .chip.bio { background: #3b1a28; } }
.progressbar { height: 8px; background: var(--line); border-radius: 99px; overflow: hidden; }
.progressbar > div { height: 100%; background: var(--saffron); }
.qtext { font-size: 1.2rem; font-weight: 600; margin: 14px 0 18px; white-space: pre-line; }
.fmt-tag { display: inline-block; font-size: .78rem; font-weight: 700; letter-spacing: .02em; padding: 2px 8px; border-radius: 6px; background: var(--navy); color: #fff; margin-top: 12px; }
.opts { display: grid; gap: 10px; }
.opt { display: flex; gap: 12px; align-items: flex-start; text-align: left; width: 100%; padding: 12px 14px; border: 1.5px solid var(--line); border-radius: 12px; background: var(--card); color: var(--ink); font: inherit; cursor: pointer; }
.opt:hover:not([disabled]) { border-color: var(--navy-2); }
.opt .key { flex: none; width: 26px; height: 26px; border-radius: 50%; border: 1.5px solid var(--line); display: grid; place-items: center; font-weight: 700; font-size: .85rem; }
.opt.sel { border-color: var(--navy-2); background: #eef2ff; }
@media (prefers-color-scheme: dark) { .opt.sel { background: #1c2a55; } }
.opt.right { border-color: var(--good); background: var(--good-bg); }
.opt.wrong { border-color: var(--bad); background: var(--bad-bg); }
.opt[disabled] { cursor: default; }
.conf { margin: 20px 0 6px; }
.conf .seg { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 6px; }
.seg button { flex: 1; min-width: 100px; padding: .6em; border-radius: 10px; border: 1.5px solid var(--line); background: var(--card); color: var(--ink); font: inherit; font-weight: 600; cursor: pointer; }
.seg button.on { background: var(--navy); border-color: var(--navy); color: #fff; }
.seg button[disabled] { cursor: default; opacity: .7; }
.panel { border-radius: 12px; padding: 14px 16px; margin-top: 16px; border: 1px solid var(--line); background: var(--card); }
.panel.mastered { background: var(--good-bg); border-color: var(--good); }
.panel.fragile { background: var(--warn-bg); border-color: var(--saffron); }
.panel.gap, .panel.misconception { background: var(--bad-bg); border-color: var(--bad); }
.panel h4 { margin: 0 0 4px; font-size: 1rem; }
.reasons { display: flex; flex-wrap: wrap; gap: 8px; margin: 8px 0; }
.reasons button { padding: .45em .9em; border-radius: 999px; border: 1.5px solid var(--line); background: var(--card); color: var(--ink); font: inherit; cursor: pointer; }
.reasons button.on { background: var(--navy); color: #fff; border-color: var(--navy); }
.mn { border-left: 4px solid var(--saffron); padding: 4px 12px; margin: 8px 0; }
.mn b { display: block; }
.bars { display: grid; gap: 10px; margin-top: 10px; }
.bar-row { display: grid; grid-template-columns: 90px 1fr 110px; gap: 10px; align-items: center; font-size: .95rem; }
.bar { height: 14px; background: var(--line); border-radius: 99px; overflow: hidden; }
.bar > div { height: 100%; background: var(--navy-2); }
table { width: 100%; border-collapse: collapse; font-size: .92rem; }
th, td { text-align: left; padding: 8px 6px; border-bottom: 1px solid var(--line); }
th { color: var(--muted); font-weight: 600; }
.flash { min-height: 190px; display: grid; place-items: center; text-align: center; padding: 24px; font-size: 1.25rem; cursor: pointer; user-select: none; }
.flash small { display: block; color: var(--muted); font-size: .85rem; margin-top: 12px; }
.slide { min-height: 320px; }
.slide ul { font-size: 1.1rem; padding-left: 1.2em; }
.slide li { margin-bottom: .6em; }
.empty { text-align: center; padding: 40px 20px; color: var(--muted); }
.kbd { font-size: .8rem; color: var(--muted); }
@media (max-width: 560px) { .bar-row { grid-template-columns: 70px 1fr 90px; } .hero { padding: 48px 0 56px; } }

/* study notes */
.note-sec { margin-top: 28px; }
.note-sec h2 { border-bottom: 2px solid var(--saffron); padding-bottom: 6px; }
.lead-note { font-size: 1.1rem; color: var(--muted); }
.toc { margin: 8px 0 0; padding-left: 1.3em; columns: 2 220px; }
.toc li { margin: 2px 0; }
.notecard { display: flex; justify-content: space-between; align-items: center; text-decoration: none; color: inherit; }
.notecard:hover { border-color: var(--saffron); }
.nb { margin: 16px 0; }
.nb-cap { font-size: .88rem; color: var(--muted); margin-top: 6px; text-align: center; }
.nb-list li { margin: 4px 0; }
.nb-table { overflow-x: auto; border: 1px solid var(--line); border-radius: 10px; }
.nb-table table { min-width: 420px; }
.nb-table th { background: var(--navy); color: #fff; text-align: left; }
.nb-table th, .nb-table td { padding: 8px 10px; border-bottom: 1px solid var(--line); vertical-align: top; }
.nb-table tbody tr:nth-child(even) { background: rgba(127,127,127,.06); }
.callout { display: flex; flex-direction: column; gap: 2px; border-left: 4px solid var(--saffron); background: var(--warn-bg); padding: 10px 14px; border-radius: 8px; margin: 14px 0; }
.callout.trap { border-color: var(--bad); background: var(--bad-bg); }
.callout.tip { border-color: var(--good); background: var(--good-bg); }
.flow { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 26px 30px; align-items: stretch; }
.flow li { position: relative; flex: 1 1 140px; max-width: 220px; background: var(--card); border: 1.5px solid var(--navy-2); border-radius: 10px; padding: 8px 10px; font-size: .93rem; text-align: center; display: flex; align-items: center; justify-content: center; }
.flow li:not(:last-child)::after { content: "→"; position: absolute; right: -24px; top: 50%; transform: translateY(-50%); color: var(--saffron-dark); font-weight: 700; font-size: 1.2rem; }
@media (max-width: 560px) {
  .flow { flex-direction: column; gap: 22px; }
  .flow li { max-width: none; }
  .flow li:not(:last-child)::after { content: "↓"; right: auto; left: 50%; top: auto; bottom: -22px; transform: translateX(-50%); }
}
.dg { width: 100%; max-width: 600px; display: block; margin: 0 auto; height: auto; }
.dg .nd { fill: var(--card); stroke: var(--navy-2); stroke-width: 1.5; }
.dg .nd-text, .dg .nd-center { fill: var(--ink); font-size: 14px; text-anchor: middle; font-family: system-ui, sans-serif; }
.dg .nd-center { font-weight: 700; font-size: 15px; fill: var(--saffron-dark); }
.dg .dg-line { fill: none; stroke: var(--muted); stroke-width: 1.6; }
.dg .dg-arrowhead { fill: var(--muted); }
.dg .dg-axis { stroke: var(--ink); stroke-width: 1.4; }
.dg .dg-axlabel { fill: var(--muted); font-size: 12px; text-anchor: middle; }
.dg .dg-curve { fill: none; stroke-width: 2.4; }
.dg .c0 { stroke: #2f5bd3; fill: #2f5bd3; } .dg .c1 { stroke: #e5534b; fill: #e5534b; } .dg .c2 { stroke: #12825a; fill: #12825a; }
.dg path.dg-curve { fill: none; }
.dg .dg-curvelabel { font-size: 12px; text-anchor: end; stroke: none; }
.dg .dg-mark { fill: var(--bad); }
.dg .dg-marklabel { fill: var(--ink); font-size: 11px; }
@media (prefers-color-scheme: dark) { .dg .c0 { stroke: #9db4ff; fill: #9db4ff; } .dg .nd { stroke: #9db4ff; } .flow li { border-color: #9db4ff; } }
.tree, .tree ul { list-style: none; margin: 0; padding-left: 22px; }
.tree { padding-left: 0; }
.tree li { position: relative; padding: 4px 0 4px 14px; }
.tree ul li::before { content: ""; position: absolute; left: -8px; top: 0; bottom: 0; border-left: 1.5px solid var(--line); }
.tree ul li::after { content: ""; position: absolute; left: -8px; top: 17px; width: 18px; border-top: 1.5px solid var(--line); }
.tree ul li:last-child::before { bottom: auto; height: 17px; }
.tn { display: inline-flex; flex-direction: column; background: var(--card); border: 1.5px solid var(--line); border-radius: 8px; padding: 4px 10px; }
.tree > li > .tn { border-color: var(--navy-2); font-weight: 700; }
.tn small { color: var(--muted); font-weight: 400; }
.formulas { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 10px; }
.fm { border: 1px solid var(--line); border-radius: 10px; padding: 10px 12px; background: var(--card); display: flex; flex-direction: column; gap: 2px; }
.fm small { color: var(--muted); }
.fm b { font-family: Georgia, serif; font-size: 1.05rem; }
.legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 4px 16px; font-size: .88rem; margin-top: 4px; }
.legend span { display: inline-flex; align-items: center; gap: 6px; }
.legend .sw { display: inline-block; width: 18px; height: 3px; border-radius: 2px; }
.legend .sw.c0 { background: #2f5bd3; } .legend .sw.c1 { background: #e5534b; } .legend .sw.c2 { background: #12825a; }
@media (prefers-color-scheme: dark) { .legend .sw.c0 { background: #9db4ff; } }
@media (prefers-color-scheme: dark) { .fmt-tag { background: var(--saffron); color: #1a1200; } }
.panel.rate textarea, #fb-text { width: 100%; font: inherit; padding: 8px 10px; border-radius: 8px; border: 1px solid var(--line); background: var(--card); color: var(--ink); }
/* Keep long chapter names inside narrow screens: selects fill their field instead of growing to the longest option. */
label.field { min-width: min(180px, 100%); }
label.field > select, label.field > input { width: 100%; min-width: 0; max-width: 100%; text-overflow: ellipsis; }

/* Learn: tutorials */
.lesson-tabs { margin: 8px 0 0; padding-left: 0; list-style: none; display: flex; flex-direction: column; gap: 4px; }
.lesson-tabs a { display: block; padding: 6px 10px; border-radius: 8px; text-decoration: none; color: inherit; }
.lesson-tabs li.on a { background: var(--warn-bg); font-weight: 600; }
.lesson-tabs li.done a { color: var(--good); }
.example { margin-top: 22px; border-left: 4px solid var(--navy-2); }
.example h3 { margin-top: 0; }
.ex-q { font-weight: 600; white-space: pre-line; margin: 0; }
.ex-steps { margin: 8px 0 0; padding-left: 1.4em; }
.ex-steps li { margin: 6px 0; white-space: pre-line; }
.ex-answer { margin-top: 10px; padding: 10px 14px; border-radius: 8px; background: var(--good-bg); }
.realcard p { margin: 6px 0 0; }
.lesson-nav { margin-top: 24px; }

/* Mock tests */
.mock-bar { position: sticky; top: 0; z-index: 5; display: flex; gap: 12px; align-items: center; justify-content: space-between; flex-wrap: wrap; background: var(--bg); padding: 10px 0; border-bottom: 1px solid var(--line); }
.mock-timer { font-variant-numeric: tabular-nums; font-weight: 700; padding: 4px 10px; border-radius: 8px; background: var(--card); border: 1px solid var(--line); }
.mock-timer.low { background: var(--bad-bg); color: var(--bad); border-color: var(--bad); }
.mock-tabs { display: flex; gap: 6px; flex-wrap: wrap; margin: 12px 0; }
.mock-tabs button { border: 1.5px solid var(--line); background: var(--card); color: var(--ink); border-radius: 999px; padding: .35em .9em; font: inherit; font-size: .9rem; cursor: pointer; }
.mock-tabs button.on { background: var(--navy); border-color: var(--navy); color: #fff; }
.mock-wrap { display: grid; grid-template-columns: minmax(0, 1fr) 280px; gap: 16px; align-items: start; }
@media (max-width: 760px) { .mock-wrap { grid-template-columns: minmax(0, 1fr); } }
.mock-actions { margin-top: 16px; }
.palette { display: grid; grid-template-columns: repeat(auto-fill, minmax(38px, 1fr)); gap: 6px; margin: 10px 0; }
.palette button { height: 34px; border-radius: 8px; border: 1.5px solid var(--line); font: inherit; font-size: .85rem; font-weight: 600; cursor: pointer; background: var(--card); color: var(--ink); }
.palette button.cur { outline: 3px solid var(--saffron); outline-offset: 1px; }
.p-a { background: var(--good) !important; border-color: var(--good) !important; color: #fff !important; }
.p-v { background: var(--bad-bg) !important; border-color: var(--bad) !important; color: var(--bad) !important; }
.p-n { background: var(--card); }
.p-m { background: #6b46c1 !important; border-color: #6b46c1 !important; color: #fff !important; }
.p-am { background: #6b46c1 !important; border-color: var(--good) !important; color: #fff !important; box-shadow: inset 0 -4px 0 var(--good); }
.legend-list { list-style: none; padding: 0; margin: 8px 0; font-size: .85rem; display: grid; gap: 4px; }
.legend-list span { display: inline-block; width: 14px; height: 14px; border-radius: 4px; border: 1.5px solid var(--line); margin-right: 8px; vertical-align: -2px; }
.badge { display: inline-block; border-radius: 6px; padding: 1px 7px; font-size: .8rem; font-weight: 700; }
.badge.ok { background: var(--good-bg); color: var(--good); } .badge.bad { background: var(--bad-bg); color: var(--bad); } .badge.skip { background: var(--line); color: var(--muted); }
.review-q { margin-top: 10px; padding: 14px 16px; }
.review-q summary { cursor: pointer; }
.small { font-size: .85rem; }


/* NEET information page */
.info-page section ul, .info-page section ol { padding-left: 1.3em; }
.info-page section li { margin: 4px 0; }
.info-page table { margin: 10px 0; }
.toc-card { margin: 16px 0; }
.flow-static { display: grid; grid-template-columns: repeat(auto-fit, minmax(170px, 1fr)); gap: 10px; margin: 12px 0; }
.flow-static div { background: var(--card); border: 1px solid var(--line); border-top: 4px solid var(--saffron); border-radius: 10px; padding: 10px 12px; display: grid; gap: 2px; }
.flow-static span { color: var(--muted); font-size: .9rem; }
.faq { margin-top: 10px; padding: 14px 16px; }
.faq summary { cursor: pointer; font-weight: 600; }
.faq p { margin: 8px 0 0; }
.tblwrap { overflow-x: auto; }

/* Question timers */
.q-timer { font: inherit; font-size: .85rem; font-variant-numeric: tabular-nums; font-weight: 600; padding: 2px 10px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); color: var(--ink); cursor: pointer; }
.q-timer.slow { border-color: var(--saffron); background: var(--warn-bg); }
.q-timer.off { color: var(--muted); font-weight: 400; }
.slow-text { color: var(--saffron-dark) !important; }
@media (prefers-color-scheme: dark) { .slow-text { color: var(--saffron) !important; } }
footer.app-footer { padding: 18px 0; margin-top: 32px; }

/* readable layouts for NEET question formats */
.q-struct { white-space: normal; font-weight: 500; font-size: 1.05rem; }
.q-struct .q-lead { font-weight: 700; font-size: 1.15rem; margin: 0 0 10px; }
.q-ask { color: var(--muted); font-weight: 600; font-size: .95rem; margin: 12px 0 0; }
.match-table { border: 1.5px solid var(--line); border-radius: 12px; border-collapse: separate; border-spacing: 0; overflow: hidden; font-size: 1rem; }
.match-table th { background: #e3ecff; color: #14224f; font-size: .85rem; letter-spacing: .04em; text-transform: uppercase; padding: 8px 12px; }
.match-table th + th { background: #fff1d6; color: #6b4500; }
.match-table td { padding: 10px 12px; vertical-align: top; border-bottom: 1px solid var(--line); }
.match-table tr:nth-child(even) td { background: rgba(127, 140, 180, .06); }
.match-table td:nth-child(3) { border-left: 2px dashed var(--line); }
.mk { display: inline-grid; place-items: center; min-width: 28px; height: 28px; padding: 0 6px; border-radius: 8px; font-weight: 800; font-size: .85rem; }
.mk-l { background: #2f5bd3; color: #fff; }
.mk-r { background: #f2a516; color: #1a1200; }
td.mk { display: table-cell; text-align: center; width: 44px; }
td.mk-l { background: #e3ecff !important; color: #1d2f6b; }
td.mk-r { background: #fff1d6 !important; color: #6b4500; }
.stmt-list { list-style: none; padding: 0; margin: 0; display: grid; gap: 8px; }
.stmt-list li { display: flex; gap: 12px; align-items: flex-start; padding: 10px 12px; border-radius: 10px; background: rgba(47, 91, 211, .06); border-left: 4px solid #2f5bd3; }
.ar-box { display: grid; gap: 4px; padding: 12px 14px; border-radius: 12px; margin: 8px 0; border-left: 5px solid; }
.ar-box b { font-size: .8rem; text-transform: uppercase; letter-spacing: .05em; }
.ar-a { background: #eef3ff; border-color: #2f5bd3; } .ar-a b { color: #2f5bd3; }
.ar-r { background: #fff6e3; border-color: #f2a516; } .ar-r b { color: #9a6200; }
.pairs { display: flex; flex-wrap: wrap; gap: 6px; }
.pair { display: inline-flex; gap: 4px; align-items: center; padding: 2px 9px; border-radius: 8px; background: rgba(47, 91, 211, .08); font-weight: 600; font-variant-numeric: tabular-nums; }
.pair b { color: #2f5bd3; }
@media (prefers-color-scheme: dark) {
  .match-table th { background: #1c2a55; color: #c9d6ff; } .match-table th + th { background: #3a2f10; color: #ffd98a; }
  td.mk-l { background: #1c2a55 !important; color: #c9d6ff; } td.mk-r { background: #3a2f10 !important; color: #ffd98a; }
  .ar-a { background: #17224a; } .ar-r { background: #2d2410; } .ar-a b { color: #9db4ff; } .ar-r b { color: #ffcf6b; }
  .stmt-list li { background: rgba(157, 180, 255, .08); } .pair b { color: #9db4ff; }
}

/* subject colours */
:root { --phy: #2f5bd3; --phy-bg: #e8efff; --che: #12825a; --che-bg: #e3f6ee; --bio: #c2185b; --bio-bg: #fde8f0; }
@media (prefers-color-scheme: dark) { :root { --phy-bg: #182650; --che-bg: #10301f; --bio-bg: #3a1526; --phy: #8fb0ff; --che: #5fd3a2; --bio: #ff8ab8; } }

/* two-level navigation */
.subnav { background: var(--navy-2); }
.subnav .wrap { display: flex; gap: 6px; flex-wrap: wrap; padding-top: 6px; padding-bottom: 6px; }
.subnav a { color: #dfe5fb; text-decoration: none; padding: .3em .9em; border-radius: 999px; font-size: .9rem; font-weight: 600; }
.subnav a:hover { background: rgba(255,255,255,.12); }
.subnav a.active { background: var(--saffron); color: #1a1200; }

/* chapters hub */
.subj-tabs { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 16px 0 8px; }
.subj-tab { display: grid; gap: 2px; padding: 12px 16px; border-radius: 14px; text-decoration: none; color: var(--ink); border: 2px solid transparent; }
.subj-tab small { color: var(--muted); }
.subj-tab.phy { background: var(--phy-bg); } .subj-tab.che { background: var(--che-bg); } .subj-tab.bio { background: var(--bio-bg); }
.subj-tab.phy.on { border-color: var(--phy); } .subj-tab.che.on { border-color: var(--che); } .subj-tab.bio.on { border-color: var(--bio); }
.subj-tab.on b { font-size: 1.1rem; }
.hub-group h2 { margin-top: 24px; }
.hub-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 12px; }
.hub-card { display: grid; gap: 6px; padding: 14px 16px; border-radius: 14px; background: var(--card); border: 1px solid var(--line); border-top: 5px solid; text-decoration: none; color: var(--ink); box-shadow: var(--shadow); transition: transform .12s; }
.hub-card:hover { transform: translateY(-2px); }
.hub-card.phy { border-top-color: var(--phy); } .hub-card.che { border-top-color: var(--che); } .hub-card.bio { border-top-color: var(--bio); }
.hub-meta { color: var(--muted); font-size: .85rem; }
.hub-bar { height: 6px; border-radius: 99px; background: var(--line); overflow: hidden; }
.hub-bar span { display: block; height: 100%; background: var(--saffron); }
.ch-head { padding: 20px 22px; border-radius: 16px; margin: 10px 0 18px; color: #fff; }
.ch-head h1 { margin: 2px 0 6px; color: #fff; } .ch-head p { margin: 0; opacity: .92; } .ch-head small { opacity: .85; font-weight: 600; }
.ch-head.phy { background: linear-gradient(135deg, #2f5bd3, #1d2f6b); }
.ch-head.che { background: linear-gradient(135deg, #12825a, #0b4d36); }
.ch-head.bio { background: linear-gradient(135deg, #c2185b, #6d1236); }
.tiles { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 12px; margin-bottom: 8px; }
.tile { display: grid; gap: 4px; padding: 16px; border-radius: 14px; text-decoration: none; color: var(--ink); border: 1px solid var(--line); background: var(--card); box-shadow: var(--shadow); }
.tile:hover { border-color: var(--navy-2); }
.tile-ic { font-size: 1.6rem; }
.tile small { color: var(--muted); }
.t-learn { background: linear-gradient(180deg, #eef3ff, var(--card)); } .t-notes { background: linear-gradient(180deg, #fff6e3, var(--card)); }
.t-slides { background: linear-gradient(180deg, #f3ecff, var(--card)); } .t-memory { background: linear-gradient(180deg, #fff0f6, var(--card)); }
.t-practice { background: linear-gradient(180deg, #e6f5ec, var(--card)); } .t-flash { background: linear-gradient(180deg, #e7f7fb, var(--card)); }
@media (prefers-color-scheme: dark) { .tile { background: var(--card) !important; } }
@media (max-width: 560px) { .subj-tabs { grid-template-columns: 1fr; } }

/* colour accents across the app */
.chip.phy { background: var(--phy-bg); color: var(--phy); font-weight: 600; }
.chip.che { background: var(--che-bg); color: var(--che); font-weight: 600; }
.chip.bio { background: var(--bio-bg); color: var(--bio); font-weight: 600; }
.opt:nth-child(1) .key { border-color: #2f5bd3; color: #2f5bd3; } .opt:nth-child(2) .key { border-color: #12825a; color: #12825a; }
.opt:nth-child(3) .key { border-color: #c2185b; color: #c2185b; } .opt:nth-child(4) .key { border-color: #b97800; color: #b97800; }
.opt.right .key { background: var(--good); border-color: var(--good); color: #fff; }
.opt.wrong .key { background: var(--bad); border-color: var(--bad); color: #fff; }
.fmt-tag { background: linear-gradient(90deg, #2f5bd3, #7b3fd9); }
.progressbar > div { background: linear-gradient(90deg, #f2a516, #e5534b); }
h1 { color: var(--navy-2); }
@media (prefers-color-scheme: dark) { h1 { color: #dfe6ff; } }
.daily-note { margin: 14px 0 0; padding: 8px 12px; border-radius: 10px; background: var(--che-bg); font-size: .92rem; }
.daily-note.low { background: var(--warn-bg); }
.daily-note b { color: var(--che); }
.qtext, .opts, .ex-q { -webkit-user-select: none; user-select: none; }
.dg .dg-tick { fill: var(--muted); font-size: 11px; }
.qtext + figure.nb, .q-struct + figure.nb { max-width: 480px; margin: 0 auto 16px; }

/* colourful diagrams */
.tree > li > .tn { background: var(--navy-2); color: #fff; border-color: var(--navy-2); }
.tree > li > .tn small { color: #dfe5fb; }
.tree > li > ul > li > .tn { border-color: #2f5bd3; background: #eef3ff; }
.tree > li > ul > li:nth-child(4n+2) > .tn { border-color: #12825a; background: #e6f5ec; }
.tree > li > ul > li:nth-child(4n+3) > .tn { border-color: #c2185b; background: #fdecf3; }
.tree > li > ul > li:nth-child(4n+4) > .tn { border-color: #b97800; background: #fff4dc; }
.tree ul ul .tn { border-color: #f2a516; background: #fffaf0; }
.flow li:nth-child(5n+1) { border-color: #2f5bd3; background: #eef3ff; }
.flow li:nth-child(5n+2) { border-color: #12825a; background: #e6f5ec; }
.flow li:nth-child(5n+3) { border-color: #7b3fd9; background: #f3ecff; }
.flow li:nth-child(5n+4) { border-color: #c2185b; background: #fdecf3; }
.flow li:nth-child(5n+5) { border-color: #b97800; background: #fff4dc; }
.fm { border-left: 4px solid #7b3fd9; background: linear-gradient(90deg, #f6f1ff, var(--card) 60%); }
.fm:nth-child(3n+2) { border-left-color: #12825a; background: linear-gradient(90deg, #eaf7f0, var(--card) 60%); }
.fm:nth-child(3n+3) { border-left-color: #2f5bd3; background: linear-gradient(90deg, #eef3ff, var(--card) 60%); }
.nb-table thead th { background: var(--navy-2); color: #fff; }
@media (prefers-color-scheme: dark) {
  .tree > li > ul > li > .tn, .tree ul ul .tn, .flow li, .fm { background: var(--card) !important; }
}
.bad-text { color: var(--bad); } .good-text { color: var(--good); }
details.mistake { margin: 8px 0; padding: 12px 16px; border-left: 4px solid var(--bad); }
details.mistake summary { cursor: pointer; font-weight: 600; }

/* Ask a doubt */
.ask-card textarea { width: 100%; font: inherit; padding: 10px 12px; border-radius: 10px; border: 1.5px solid var(--line); background: var(--card); color: var(--ink); }
.ask-card textarea:focus { outline: 2px solid var(--saffron); border-color: transparent; }
.about-q { background: var(--warn-bg); border-radius: 10px; padding: 10px 12px; margin-bottom: 12px; }
.about-q p { margin: 4px 0 0; }
.suggestions h3 { margin-top: 18px; font-size: 1.15rem; }
.sugg { border: 1px solid var(--line); border-left: 4px solid var(--navy-2); border-radius: 10px; padding: 10px 14px; margin: 10px 0; background: var(--card); }
.sugg.card-sugg { border-left-color: var(--che); } .sugg.mn-sugg { border-left-color: var(--saffron); } .sugg.q-sugg { border-left-color: var(--bio); }
.sugg p { margin: 4px 0; } .sugg b { display: block; margin-top: 4px; }
.sugg .tag, .about-q .tag { font-size: .75rem; font-weight: 700; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); }
details.doubt { border: 1px solid var(--line); border-radius: 12px; padding: 10px 14px; margin: 10px 0; background: var(--card); }
details.doubt summary { cursor: pointer; font-weight: 600; }
details.doubt .badge { font-size: .8rem; padding: 2px 8px; border-radius: 999px; background: var(--warn-bg); white-space: nowrap; }
details.doubt.answered .badge { background: var(--good-bg); color: var(--good); }
.doubt-q { white-space: pre-wrap; }
.doubt-a { background: var(--good-bg); border-radius: 10px; padding: 10px 12px; }
.doubt-a p { margin: 4px 0 0; white-space: pre-wrap; }
.ask-link { margin-top: 12px; }
.sugg .qtext { font-size: 1rem; font-weight: 600; margin: 4px 0; }
.sugg b { font-weight: 700; }

/* Static chapter pages (SEO) */
.seo-page { padding-block: 24px 48px; max-width: 900px; }
.seo-page section { margin-top: 32px; }
.seo-page h1 { font-size: clamp(1.8rem, 4.5vw, 2.6rem); }
.seo-h1.phy, h2.phy { color: var(--phy); } .seo-h1.che, h2.che { color: var(--che); } .seo-h1.bio, h2.bio { color: var(--bio); }
.crumbs { font-size: .9rem; color: var(--muted); margin-bottom: 12px; }
.facts { display: flex; flex-wrap: wrap; gap: 8px; margin: 12px 0 18px; }
.facts span { background: var(--card); border: 1px solid var(--line); border-radius: 999px; padding: 3px 12px; font-size: .9rem; }
.lessons li { margin: 8px 0; }
.mn-card { border: 1px solid var(--line); border-left: 4px solid var(--saffron); border-radius: 10px; padding: 10px 14px; margin: 10px 0; background: var(--card); }
.mn-card .tag { display: block; font-size: .75rem; font-weight: 700; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); }
.mn-card b { display: block; font-size: 1.05rem; margin: 2px 0; } .mn-card p { margin: 4px 0 0; }
.sample-q { border: 1px solid var(--line); border-radius: 12px; padding: 12px 16px; margin: 12px 0; background: var(--card); }
.sample-q p { white-space: pre-line; margin: 6px 0; } .sample-q ol { margin: 6px 0; padding-left: 1.4em; }
.sample-q summary { cursor: pointer; font-weight: 600; color: var(--navy-2); }
.seo-page th { text-align: left; white-space: nowrap; padding-right: 12px; }
.ch-list { columns: 2 260px; padding-left: 1.1em; } .ch-list li { margin: 4px 0; break-inside: avoid; }
.related a { white-space: nowrap; }
.note-box { background: var(--warn-bg); border-radius: 10px; padding: 10px 14px; }
@media (prefers-color-scheme: dark) { .sample-q summary { color: #9db4ff; } }

/* ---------- Colour pass 2 (Nov 2026): contrast fixes and a richer palette ---------- */
/* Stronger text shades of the subject colours, so coloured text passes WCAG AA (4.5:1) on its tint. */
:root { --phy-ink: #2449b8; --che-ink: #0b6b47; --bio-ink: #a3134e; --amber-ink: #855400; }
@media (prefers-color-scheme: dark) { :root { --phy-ink: #9db4ff; --che-ink: #6fe0b0; --bio-ink: #ff9cc4; --amber-ink: #ffd27a; } }
.chip.phy { color: var(--phy-ink); } .chip.che { color: var(--che-ink); } .chip.bio { color: var(--bio-ink); }
.daily-note b { color: var(--che-ink); }
.opt:nth-child(1) .key { border-color: var(--phy-ink); color: var(--phy-ink); }
.opt:nth-child(2) .key { border-color: var(--che-ink); color: var(--che-ink); }
.opt:nth-child(3) .key { border-color: var(--bio-ink); color: var(--bio-ink); }
.opt:nth-child(4) .key { border-color: var(--amber-ink); color: var(--amber-ink); }
.opt.right .key { background: var(--good); border-color: var(--good); color: #fff; }
.opt.wrong .key { background: var(--bad); border-color: var(--bad); color: #fff; }

/* Home page banner: white headline with a saffron second line, and a soft glow of the three subject colours. */
.hero { background:
  radial-gradient(600px 300px at 85% 10%, rgba(47, 91, 211, .45), transparent 70%),
  radial-gradient(500px 260px at 10% 100%, rgba(194, 24, 91, .30), transparent 70%),
  radial-gradient(420px 220px at 60% 110%, rgba(18, 130, 90, .30), transparent 70%),
  linear-gradient(160deg, #101b44, #1d2f6b); }
.hero h1 { color: #fff; }
.hero h1 .accent { color: var(--saffron); }
.hero .stat b { color: #fff; }

/* Colour-coded steps and feature cards on the home page. */
#how .card:nth-child(4n+1) .step-num { background: #2f5bd3; color: #fff; }
#how .card:nth-child(4n+2) .step-num { background: #12825a; color: #fff; }
#how .card:nth-child(4n+3) .step-num { background: #c2185b; color: #fff; }
#how .card:nth-child(4n+4) .step-num { background: var(--saffron); color: #1a1200; }
#features .card { border-top: 4px solid var(--saffron); }
#features .card:nth-child(4n+1) { border-top-color: #2f5bd3; }
#features .card:nth-child(4n+2) { border-top-color: #12825a; }
#features .card:nth-child(4n+3) { border-top-color: #c2185b; }

/* Headings inside dark banners always stay light. */
.hero h1, .hero h2, .ch-head h1, .ch-head h2 { color: #fff; }

/* Confidence report */
.conf-tiles { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 12px 0; }
@media (max-width: 560px) { .conf-tiles { grid-template-columns: repeat(2, 1fr); } }
.conf-tile { border-radius: 12px; padding: 10px 12px; border: 1px solid var(--line); background: var(--card); }
.conf-tile b { display: block; font-size: 1.6rem; font-family: Georgia, serif; }
.conf-tile span { font-size: .88rem; }
.conf-tile.good { border-left: 5px solid var(--good); } .conf-tile.good b { color: var(--good); }
.conf-tile.bad { border-left: 5px solid var(--bad); } .conf-tile.bad b { color: var(--bad); }

.lang-note { font-size: .85rem; color: var(--muted); background: var(--warn-bg); border-radius: 8px; padding: 4px 10px; display: inline-block; margin: 6px 0 0; }

/* Sign-in and account */
.auth-wrap { max-width: 640px; margin: 0 auto; }
.auth-wrap input[type="email"], .auth-wrap input[type="text"], .auth-wrap input[type="tel"] { width: 100%; font: inherit; padding: .55em .7em; border: 1.5px solid var(--line); border-radius: 10px; background: var(--card); color: var(--ink); }
.form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
@media (max-width: 560px) { .form-grid { grid-template-columns: 1fr; } }
label.check { align-items: flex-start; gap: 8px; margin: 6px 0; font-weight: 400; flex-wrap: nowrap; }
label.check input { margin-top: 4px; flex: none; }
.account-card summary { cursor: pointer; }

/* Encouragement messages */
.cheer { display: flex; gap: 10px; align-items: flex-start; margin: 14px 0; padding: 12px 14px; border-radius: 12px;
  background: linear-gradient(90deg, var(--warn-bg), var(--card)); border: 1px solid var(--line); border-left: 5px solid var(--saffron); font-weight: 500; }
.cheer-icon { font-size: 1.2rem; line-height: 1.3; }
.nav a.home-link { font-weight: 700; }

/* Concept deep dives */
details.concept { border: 1px solid var(--line); border-left: 5px solid var(--navy-2); border-radius: 12px; padding: 10px 14px; margin: 14px 0; background: var(--card); }
details.concept summary { cursor: pointer; }
details.concept .concept-badge { font-size: .78rem; font-weight: 700; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); }
details.concept h4 { margin: 14px 0 4px; }
details.concept ul { margin: 4px 0; padding-left: 1.3em; }
.concept-summary { font-weight: 600; margin: 10px 0 4px; }
.concept-ex { background: var(--bg); border-radius: 10px; padding: 8px 12px; margin: 8px 0; }
.concept-result { margin: 4px 0 0; }
.concept-tip { background: var(--warn-bg); border-radius: 10px; padding: 8px 12px; margin: 12px 0 2px; }