/* Learn with Vipul Sir - shared styles for every page under /learn/.
   Loaded after ../styles.css, so it reuses the site's colours, header, buttons and footer. */

.site-header.is-static { position: relative; background: var(--paper); }
.nav-links a[aria-current]::after { right: 0; }

.learn-wrap { max-width: 1180px; margin: 0 auto; padding: 0 clamp(22px, 5vw, 48px); }

/* Breadcrumbs */
.breadcrumbs { padding-top: 34px; }
.breadcrumbs ol { list-style: none; display: flex; flex-wrap: wrap; gap: 8px; padding: 0; margin: 0; font-size: 12px; font-weight: 700; color: var(--muted); }
.breadcrumbs li + li::before { content: "›"; margin-right: 8px; color: var(--orange); }
.breadcrumbs a:hover { color: var(--orange); }

/* Page hero */
.learn-hero { padding: 30px 0 52px; border-bottom: 1px solid var(--line); }
.learn-hero h1 { font-size: clamp(38px, 5.4vw, 74px); line-height: .98; letter-spacing: -.055em; font-weight: 900; margin: 16px 0 0; max-width: 960px; }
.learn-hero h1 em { color: var(--orange); font-style: normal; }
.learn-lede { font-size: clamp(17px, 1.4vw, 20px); color: var(--muted); line-height: 1.6; max-width: 720px; margin: 22px 0 0; }

.answer-box { margin-top: 30px; max-width: 840px; background: white; border: 1px solid var(--line); border-left: 6px solid var(--orange); border-radius: 18px; padding: 22px 26px; font-size: 17px; line-height: 1.7; }
.answer-box p { margin: 0 0 10px; }
.answer-box p:last-child { margin-bottom: 0; }
.box-label { display: block; font-size: 10px; letter-spacing: .14em; text-transform: uppercase; font-weight: 900; color: var(--orange); margin-bottom: 8px; }

.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 22px; }
.chip { font-size: 11px; font-weight: 800; letter-spacing: .03em; padding: 6px 11px; border-radius: 999px; background: var(--mint); color: var(--ink); }

.byline { display: flex; align-items: center; gap: 12px; margin-top: 26px; font-size: 13px; color: var(--muted); }
.byline img { width: 42px; height: 42px; border-radius: 50%; object-fit: cover; }
.byline strong { color: var(--ink); }

/* Lesson layout: article + sticky sidebar */
.lesson-layout { display: grid; grid-template-columns: minmax(0, 1fr) 280px; gap: clamp(40px, 6vw, 80px); padding: 56px 0 90px; align-items: start; }
.lesson-body { min-width: 0; max-width: 760px; font-size: 17px; line-height: 1.75; }
.lesson-body h2 { font-size: clamp(28px, 3vw, 40px); letter-spacing: -.045em; line-height: 1.05; margin: 0 0 18px; }
.lesson-body > section { padding-top: 64px; }
.lesson-body > section:first-child { padding-top: 0; }
.lesson-body section[id] { scroll-margin-top: 12px; }
.lesson-body h3 { font-size: 20px; letter-spacing: -.02em; line-height: 1.3; margin: 34px 0 10px; }
.lesson-body p { margin: 0 0 18px; }
.lesson-body ul, .lesson-body ol { padding-left: 22px; margin: 0 0 18px; }
.lesson-body li { margin-bottom: 8px; }
.lesson-body a:not(.button) { color: var(--orange-dark); text-decoration: underline; text-underline-offset: 3px; }
.h2-kicker { display: block; font-size: 11px; font-weight: 900; letter-spacing: .14em; text-transform: uppercase; color: var(--orange); margin-bottom: 10px; }

.katex { font-size: 1.08em; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 6px 0; margin: 14px 0; }

.rule-box { background: var(--ink); color: white; border-radius: 22px; padding: 28px 30px; margin: 26px 0; }
.rule-box .box-label { color: var(--mint); }
.rule-box h3 { color: white; margin: 24px 0 2px; font-size: 15px; letter-spacing: 0; }
.rule-box h3:first-of-type { margin-top: 6px; }
.rule-box p { color: rgba(255,255,255,.78); margin: 0; }

.tip { background: #fffdf8; border: 1px dashed var(--orange); border-radius: 18px; padding: 18px 22px; margin: 26px 0; }
.tip p { margin: 0; }

/* Tables */
.table-wrap { overflow-x: auto; margin: 22px 0 26px; border: 1px solid var(--line); border-radius: 18px; background: white; }
.learn-table { width: 100%; border-collapse: collapse; font-size: 15px; }
.learn-table th, .learn-table td { padding: 12px 16px; text-align: left; border-bottom: 1px solid var(--line); vertical-align: middle; }
.learn-table th { font-size: 10px; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); background: #fffdf8; }
.learn-table tr:last-child td { border-bottom: 0; }

/* Diagrams (inline SVG) */
.diagram { margin: 26px 0; background: white; border: 1px solid var(--line); border-radius: 22px; padding: 18px 18px 14px; }
.diagram svg { width: 100%; height: auto; display: block; }
.diagram figcaption { font-size: 14px; line-height: 1.6; color: var(--muted); padding: 10px 6px 0; }
.diagram text { font-family: Arial, Helvetica, sans-serif; font-size: 16px; fill: var(--ink); }
.diagram .label-muted { fill: var(--muted); font-size: 14px; }
.diagram .label-accent { fill: var(--orange-dark); font-weight: 700; }
.diagram .label-green { fill: #11804d; font-weight: 700; }
.diagram .axis { stroke: var(--muted); stroke-width: 1.5; }
.diagram .guide { stroke: var(--muted); stroke-width: 1.2; stroke-dasharray: 3 5; }
.diagram .curve { stroke: var(--ink); stroke-width: 3.5; fill: none; }
.diagram .tangent { stroke: var(--orange); stroke-width: 3; }
.diagram .secant { stroke: #17a966; stroke-width: 2.5; }
.diagram .delta { stroke: var(--ink); stroke-width: 1.5; stroke-dasharray: 6 5; }
.diagram .point { fill: var(--orange); }
.diagram .node { fill: var(--paper); stroke: var(--ink); stroke-width: 2; }
.diagram .node-text { font-size: 26px; font-weight: 900; }
.diagram .link { stroke: var(--ink); stroke-width: 2; fill: none; }
.diagram .link-accent { stroke: var(--orange); stroke-width: 2.5; fill: none; }
.diagram .head { fill: var(--ink); }
.diagram .head-accent { fill: var(--orange); }

/* Worked examples */
.example { background: white; border: 1px solid var(--line); border-radius: 22px; padding: 26px 28px; margin: 20px 0; }
.example-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 8px; }
.example-head h3 { margin: 0; font-size: 18px; }
.level { flex: 0 0 auto; font-size: 10px; font-weight: 900; letter-spacing: .1em; text-transform: uppercase; padding: 5px 10px; border-radius: 999px; }
.level.easy { background: var(--mint); }
.level.medium { background: #ffe4a8; }
.level.exam { background: var(--orange); color: white; }
.example .question { font-size: 18px; margin-bottom: 14px; }
.lesson-body .steps { counter-reset: step; list-style: none; padding: 0; margin: 0 0 14px; }
.steps li { counter-increment: step; position: relative; padding-left: 40px; margin-bottom: 12px; }
.steps li::before { content: counter(step); position: absolute; left: 0; top: 3px; width: 26px; height: 26px; border-radius: 50%; background: var(--paper); border: 1px solid var(--line); display: grid; place-items: center; font-size: 12px; font-weight: 900; }
.lesson-body .answer-line { border-top: 1px solid var(--line); padding-top: 14px; margin: 0; font-weight: 700; }
.answer-line .box-label { display: inline; margin-right: 10px; }

/* Common mistakes */
.mistakes { display: grid; gap: 14px; margin: 22px 0; }
.mistake { background: white; border: 1px solid var(--line); border-radius: 18px; padding: 20px 22px; }
.mistake h3 { margin: 0 0 10px; font-size: 17px; }
.lesson-body .mistake p { margin: 8px 0 0; font-size: 15px; color: var(--muted); }
.lesson-body .mistake .wrong, .lesson-body .mistake .right, .lesson-body .mistake .compare { color: var(--ink); font-size: 17px; }
.wrong, .right, .compare { display: flex; gap: 12px; align-items: center; padding: 8px 0; line-height: 1.5; }
.mistake h3 + .wrong, .mistake h3 + .compare { padding-top: 2px; }
.wrong::before, .right::before, .compare::before { flex: 0 0 18px; font-weight: 900; }
.wrong::before { content: "✗"; color: #c0392b; }
.right::before { content: "✓"; color: #17a966; }
.compare::before { content: "→"; color: var(--orange); }

/* Practice questions */
details.practice { background: white; border: 1px solid var(--line); border-radius: 16px; margin: 12px 0; }
details.practice summary { cursor: pointer; padding: 16px 20px; list-style: none; display: flex; gap: 14px; align-items: baseline; }
details.practice summary::-webkit-details-marker { display: none; }
.q-num { flex: 0 0 auto; font-weight: 900; color: var(--orange); font-size: 12px; }
.reveal { margin-left: auto; flex: 0 0 auto; font-size: 11px; font-weight: 800; color: var(--muted); white-space: nowrap; }
.reveal::before { content: "Show answer +"; }
details[open] .reveal::before { content: "Hide answer −"; }
.practice-answer { padding: 14px 20px 18px; border-top: 1px solid var(--line); }
.lesson-body .practice-answer p { margin: 0 0 10px; }
.lesson-body .practice-answer p:last-child { margin-bottom: 0; }

/* FAQ */
.faq details { border-bottom: 1px solid var(--line); padding: 18px 0; }
.faq details:first-child { border-top: 1px solid var(--line); }
.faq summary { cursor: pointer; font-weight: 800; font-size: 17px; list-style: none; display: flex; justify-content: space-between; gap: 16px; }
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; color: var(--orange); font-size: 22px; line-height: 1; }
.faq details[open] summary::after { content: "−"; }
.faq details p { margin: 12px 0 0; color: var(--muted); line-height: 1.7; }

/* Related lessons, pager, author */
.lesson-body .related-list { list-style: none; padding: 0; display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.related-list li { margin: 0; border: 1px solid var(--line); border-radius: 14px; padding: 12px 16px; font-size: 15px; font-weight: 700; display: flex; justify-content: space-between; gap: 10px; align-items: center; background: rgba(255,255,255,.5); }
.soon { flex: 0 0 auto; font-size: 10px; font-weight: 900; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); }

.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 56px; }
.pager > * { border: 1px solid var(--line); border-radius: 18px; padding: 18px 20px; display: grid; gap: 4px; background: white; font-size: 16px; font-weight: 700; }
.pager small { font-size: 10px; letter-spacing: .12em; text-transform: uppercase; font-weight: 900; color: var(--muted); }
.pager .next { text-align: right; }
.pager .is-soon { background: transparent; color: var(--muted); }
.lesson-body .pager a { color: var(--ink); text-decoration: none; }
.pager a:hover { border-color: var(--orange); }
.lesson-body .back-link { display: inline-block; margin-top: 18px; font-size: 14px; font-weight: 800; }

.author-box { display: flex; gap: 20px; align-items: flex-start; border-top: 1px solid var(--line); padding-top: 32px; margin-top: 56px; }
.author-box img { width: 76px; height: 76px; border-radius: 50%; object-fit: cover; flex: 0 0 auto; }
.author-box strong { font-size: 18px; }
.lesson-body .author-box p, .author-box p { font-size: 15px; line-height: 1.65; color: var(--muted); margin: 6px 0 0; }

/* Sidebar */
.lesson-aside { position: sticky; top: 24px; display: grid; gap: 16px; }
.toc { border: 1px solid var(--line); border-radius: 20px; padding: 20px 22px; background: rgba(255,255,255,.55); }
.toc ol { list-style: none; padding: 0; margin: 12px 0 0; display: grid; gap: 10px; font-size: 13px; font-weight: 700; }
.toc a { color: var(--muted); display: block; border-left: 2px solid transparent; padding-left: 10px; margin-left: -12px; }
.toc a:hover, .toc a.is-active { color: var(--ink); border-left-color: var(--orange); }
.aside-cta { background: var(--ink); color: white; border-radius: 20px; padding: 24px; }
.aside-cta strong { font-size: 22px; letter-spacing: -.03em; line-height: 1.15; display: block; }
.aside-cta p { color: rgba(255,255,255,.7); font-size: 13px; line-height: 1.6; margin: 10px 0 16px; }
.aside-cta .button { min-height: 46px; width: 100%; }
.aside-cta .button.primary span { margin-left: 10px; font-size: 15px; }

/* Full-width call to action */
.author-box + .learn-cta { margin-top: 64px; }
.learn-cta { background: var(--mint); border-radius: 30px; padding: clamp(36px, 5vw, 64px); text-align: center; margin: 0 0 90px; }
.learn-cta h2 { font-size: clamp(32px, 4vw, 54px); letter-spacing: -.05em; line-height: 1; margin: 12px auto 0; max-width: 720px; }
.learn-cta p { color: var(--muted); max-width: 600px; margin: 18px auto 28px; line-height: 1.7; }

/* Topic guide (pillar) page */
.pillar-section { padding-top: 84px; }
.group-head { display: grid; grid-template-columns: 1fr 1fr; gap: 40px; align-items: end; margin-bottom: 26px; }
.group-head h2 { font-size: clamp(32px, 4vw, 52px); letter-spacing: -.05em; margin: 10px 0 0; line-height: 1; }
.group-head p { color: var(--muted); line-height: 1.7; margin: 0; }
.pillar-section[id] { scroll-margin-top: 12px; }

.roadmap { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }
.level-card { background: white; border: 1px solid var(--line); border-radius: 22px; padding: 24px; display: flex; flex-direction: column; min-height: 290px; transition: transform .2s, box-shadow .2s; }
.level-card:hover { transform: translateY(-4px); box-shadow: 0 18px 45px rgba(16,42,43,.08); }
.level-card .step { font-size: 11px; font-weight: 900; color: var(--orange); letter-spacing: .1em; }
.level-card h3 { font-size: 23px; letter-spacing: -.03em; margin: 16px 0 6px; }
.level-card .boards { font-size: 10px; font-weight: 800; color: var(--muted); text-transform: uppercase; letter-spacing: .08em; }
.level-card p { font-size: 14px; color: var(--muted); line-height: 1.6; margin: 14px 0 18px; }
.level-card .go { margin-top: auto; font-weight: 900; font-size: 13px; }
.level-card .go span { color: var(--orange); margin-left: 6px; }

.explainer { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: clamp(30px, 5vw, 64px); align-items: start; font-size: 17px; line-height: 1.75; }
.explainer p { margin: 0 0 18px; }
.explainer .diagram, .explainer .answer-box { margin-top: 0; }
.explainer a { color: var(--orange-dark); text-decoration: underline; text-underline-offset: 3px; }

.formula-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.formula-grid .table-wrap { margin: 0; }
.formula-note { font-size: 14px; color: var(--muted); margin: 14px 0 0; }
.formula-note a { color: var(--orange-dark); text-decoration: underline; text-underline-offset: 3px; }

.lesson-list { list-style: none; padding: 0; margin: 0; border-top: 1px solid var(--line); }
.lesson-item { border-bottom: 1px solid var(--line); }
.lesson-row { display: grid; grid-template-columns: 44px minmax(0, 1fr) auto; gap: 18px; align-items: center; padding: 18px 8px; transition: background .2s; }
.lesson-item.is-live .lesson-row { background: rgba(255,255,255,.55); }
.lesson-item.is-live .lesson-row:hover { background: white; }
.lesson-row .n { font-size: 11px; font-weight: 900; color: var(--muted); }
.lesson-row strong { font-size: 18px; letter-spacing: -.02em; }
.lesson-item:not(.is-live) strong { color: rgba(16,42,43,.72); }
.lesson-row p { margin: 4px 0 0; font-size: 14px; line-height: 1.5; color: var(--muted); }
.tags { display: flex; gap: 6px; flex-wrap: wrap; margin-top: 8px; }
.tag { font-size: 10px; font-weight: 800; padding: 3px 8px; border-radius: 999px; border: 1px solid var(--line); color: var(--muted); }
.status { font-size: 11px; font-weight: 900; white-space: nowrap; }
.status.live { background: var(--orange); color: white; padding: 9px 15px; border-radius: 999px; }
.status.soon-status { color: var(--muted); letter-spacing: .06em; text-transform: uppercase; font-size: 10px; }

.faq-wrap { max-width: 820px; }

/* Learn home */
.feature-grid { display: grid; grid-template-columns: 1.35fr 1fr; gap: 16px; }
.feature-grid.even { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.feature-card { border-radius: 26px; padding: clamp(28px, 4vw, 48px); display: flex; flex-direction: column; min-height: 360px; border: 1px solid var(--line); background: white; transition: transform .2s, box-shadow .2s; }
.feature-card:hover { transform: translateY(-4px); box-shadow: 0 18px 45px rgba(16,42,43,.1); }
.feature-card.dark { background: var(--ink); color: white; border-color: var(--ink); }
.feature-card .box-label { margin-bottom: 0; }
.feature-card.dark .box-label { color: var(--mint); }
.feature-card .symbol { font-size: 44px; font-weight: 900; letter-spacing: -.04em; margin: 26px 0 auto; color: var(--orange); }
.feature-card h3 { font-size: clamp(28px, 3vw, 42px); letter-spacing: -.045em; line-height: 1.02; margin: 26px 0 12px; }
.feature-card p { color: var(--muted); line-height: 1.65; margin: 0 0 24px; max-width: 520px; }
.feature-card.dark p { color: rgba(255,255,255,.7); }
.feature-card .go { font-weight: 900; font-size: 14px; }
.feature-card .go span { color: var(--orange); margin-left: 8px; }

.topic-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
.topic-card { border: 1px solid var(--line); border-radius: 18px; padding: 20px 22px; display: flex; justify-content: space-between; align-items: center; gap: 12px; background: rgba(255,255,255,.5); }
.topic-card strong { font-size: 17px; letter-spacing: -.02em; }
.topic-card small { display: block; font-size: 12px; color: var(--muted); margin-top: 4px; line-height: 1.5; }

.how-grid { list-style: none; padding: 0; margin: 0; display: grid; grid-template-columns: repeat(5, 1fr); gap: 16px; counter-reset: how; }
.how-grid li { counter-increment: how; border-top: 3px solid var(--ink); padding-top: 16px; }
.how-grid li::before { content: "0" counter(how); display: block; font-size: 11px; font-weight: 900; color: var(--orange); letter-spacing: .1em; margin-bottom: 10px; }
.how-grid strong { font-size: 17px; }
.how-grid p { font-size: 14px; color: var(--muted); line-height: 1.6; margin: 6px 0 0; }

.home-sections { padding-bottom: 84px; }


/* Subject (service) pages, e.g. /subjects/calculus/ */
.learn-hero .hero-actions { margin-top: 30px; }
.fact-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 16px; margin-top: 40px; }
.fact { border-top: 3px solid var(--ink); padding-top: 14px; }
.fact span { display: block; font-size: 10px; font-weight: 900; letter-spacing: .12em; text-transform: uppercase; color: var(--orange); margin-bottom: 6px; }
.fact strong { font-size: 17px; letter-spacing: -.02em; line-height: 1.35; }
.use-grid, .unit-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 14px; }
.use-card { background: white; border: 1px solid var(--line); border-radius: 20px; padding: 24px; }
.use-card strong { font-size: 19px; letter-spacing: -.02em; }
.use-card p { font-size: 14px; color: var(--muted); line-height: 1.65; margin: 8px 0 0; }
.unit-card { background: white; border: 1px solid var(--line); border-radius: 22px; padding: 24px; display: flex; flex-direction: column; min-height: 220px; transition: transform .2s, box-shadow .2s; }
.unit-card:hover { transform: translateY(-4px); box-shadow: 0 18px 45px rgba(16,42,43,.08); }
.unit-card .step { font-size: 11px; font-weight: 900; color: var(--orange); letter-spacing: .1em; }
.unit-card h3 { font-size: 21px; letter-spacing: -.03em; line-height: 1.15; margin: 14px 0 8px; }
.unit-card p { font-size: 14px; color: var(--muted); line-height: 1.6; margin: 0 0 16px; }
.unit-card .go { margin-top: auto; font-weight: 900; font-size: 12px; color: var(--muted); letter-spacing: .06em; text-transform: uppercase; }
.unit-block { margin-top: 44px; scroll-margin-top: 12px; }
.unit-block:first-of-type { margin-top: 0; }
.unit-head { display: flex; align-items: baseline; justify-content: space-between; gap: 16px; margin-bottom: 12px; }
.unit-head h3 { font-size: clamp(22px, 2.4vw, 30px); letter-spacing: -.04em; margin: 6px 0 0; }
.unit-head .kicker { margin: 0; }
.unit-head .count { font-size: 12px; font-weight: 800; color: var(--muted); white-space: nowrap; }
.prereq { background: white; border: 1px solid var(--line); border-left: 6px solid var(--mint); border-radius: 16px; padding: 16px 20px; margin: 0 0 36px; font-size: 15px; line-height: 1.6; max-width: 860px; }
.prereq a, .group-head p a { color: var(--orange-dark); text-decoration: underline; text-underline-offset: 3px; }
.how-grid.four { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.check-list { list-style: none; padding: 0; margin: 0; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.check-list li { background: white; border: 1px solid var(--line); border-radius: 16px; padding: 16px 18px; font-weight: 700; display: flex; gap: 12px; line-height: 1.5; }
.check-list li::before { content: "✓"; color: #17a966; font-weight: 900; }
.lesson-body .prereq { margin: 0 0 8px; }

@media (max-width: 980px) {
  .lesson-layout { grid-template-columns: minmax(0, 1fr); padding-top: 40px; }
  .lesson-aside { display: none; }
  .roadmap { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .explainer, .feature-grid, .feature-grid.even { grid-template-columns: minmax(0, 1fr); }
  .how-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 22px 16px; }
  .topic-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .fact-grid, .use-grid, .unit-grid, .how-grid.four { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 700px) {
  .group-head { grid-template-columns: minmax(0, 1fr); gap: 14px; }
  .roadmap, .formula-grid, .topic-grid, .pager { grid-template-columns: minmax(0, 1fr); }
  .lesson-body .related-list { grid-template-columns: minmax(0, 1fr); }
  .level-card { min-height: 0; }
  .lesson-row { grid-template-columns: 30px minmax(0, 1fr); gap: 12px; }
  .lesson-row .status { grid-column: 2; justify-self: start; }
  .example { padding: 22px 18px; }
  .rule-box { padding: 24px 20px; }
  .answer-box { padding: 18px 18px 18px 20px; }
  .pager .next { text-align: left; }
  .author-box { flex-direction: column; }
  .learn-cta { border-radius: 22px; margin-bottom: 60px; }
  .fact-grid, .use-grid, .unit-grid, .how-grid.four, .check-list { grid-template-columns: minmax(0, 1fr); }
  .unit-card { min-height: 0; }
  .unit-head { flex-direction: column; gap: 4px; }
}