:root{--bg: #f6f8fc;--surface: #ffffff;--surface-2: #eef2f8;--surface-3: #e2e8f4;--ink: #0b1329;--ink-light: #2d3a5a;--muted: #5f6f94;--line: #e0e7f3;--line-strong: #c5d2e8;--shadow-sm: 0 1px 3px rgba(11,19,41,.06), 0 1px 2px rgba(11,19,41,.04);--shadow: 0 10px 25px -5px rgba(11,19,41,.08), 0 8px 10px -6px rgba(11,19,41,.04);--shadow-lg: 0 20px 30px -10px rgba(11,19,41,.14);--accent: #0284c7;--accent-soft: #e0f2fe;--learn: #4f46e5;--learn-bg: #eef2ff;--learn-border: #c7d2fe;--quiz: #d97706;--quiz-bg: #fffbeb;--quiz-border: #fde68a;--ncert: #0891b2;--ncert-bg: #ecfeff;--ncert-border: #a5f3fc;--revision: #9333ea;--revision-bg: #faf5ff;--revision-border: #e9d5ff;--pyq: #ea580c;--pyq-bg: #fff7ed;--pyq-border: #fed7aa;--test: #0284c7;--test-bg: #f0f9ff;--test-border: #bae6fd;--ok: #059669;--ok-bg: #ecfdf5;--ok-border: #a7f3d0;--danger: #e11d48;--danger-bg: #fff1f2;--danger-border: #fecdd3;--radius-sm: 8px;--radius: 16px;--radius-lg: 22px;--nav-h: 68px}*{box-sizing:border-box;margin:0;padding:0}html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}body{background:var(--bg);color:var(--ink);font-family:Roboto,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;line-height:1.65;font-size:14.5px;letter-spacing:0;padding-bottom:calc(var(--nav-h) + 28px);-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}button,input{font:inherit}button{cursor:pointer}.app{width:100%;max-width:880px;margin:0 auto;padding:0 14px}.hub-breadcrumbs{display:flex!important;align-items:center!important;gap:8px!important;font-size:.8rem!important;color:var(--muted)!important;margin-bottom:12px!important;font-weight:500!important;flex-wrap:wrap!important}.hub-breadcrumbs a{color:var(--muted)!important;text-decoration:none!important;display:inline-flex!important;align-items:center!important;gap:5px!important;transition:color .2s ease!important}.hub-breadcrumbs a:hover{color:var(--learn)!important}.hub-breadcrumbs .crumb-active{color:var(--ink)!important;font-weight:700!important}header{padding:22px 2px 10px;display:flex;flex-direction:column;gap:6px}.eyebrow{display:flex;align-items:center;gap:8px;flex-wrap:wrap;font-size:11px;font-weight:800;letter-spacing:.1em;text-transform:uppercase;color:var(--learn)}.badge-year{background:linear-gradient(135deg,#4f46e5,#06b6d4);color:#fff;padding:2px 8px;border-radius:99px;font-size:9.5px;font-weight:700;letter-spacing:.04em}h1{font-family:Roboto Slab,Roboto,serif;font-size:28px;line-height:1.24;letter-spacing:-.02em;font-weight:700;color:var(--ink)}.subtitle{color:var(--muted);font-size:14px;line-height:1.55}.progress-wrap{background:var(--surface-3);border-radius:99px;height:4px;overflow:hidden;margin:10px 0 16px}.progress-bar{height:100%;width:16%;background:linear-gradient(90deg,#4f46e5,#0891b2,#9333ea,#ea580c,#0284c7);transition:width .3s ease}.tab{display:none;padding:6px 0 28px}.tab.active{display:block}.hero-card{border-radius:var(--radius-lg);padding:18px 16px;margin-bottom:18px;position:relative;overflow:hidden;border:1px solid transparent;box-shadow:var(--shadow-sm)}.hero-card.learn{background:linear-gradient(135deg,#eef2ff,#e0e7ff);border-color:var(--learn-border)}.hero-card.quiz{background:linear-gradient(135deg,#fffbeb,#fef3c7);border-color:var(--quiz-border)}.hero-card.exercise{background:linear-gradient(135deg,#ecfeff,#cffafe);border-color:var(--ncert-border)}.hero-card.revision{background:linear-gradient(135deg,#faf5ff,#f3e8ff);border-color:var(--revision-border)}.hero-card.pyqs{background:linear-gradient(135deg,#fff7ed,#ffedd5);border-color:var(--pyq-border)}.hero-card.tests{background:linear-gradient(135deg,#f0f9ff,#e0f2fe);border-color:var(--test-border)}.hero-kicker{font-size:9.5px;font-weight:800;letter-spacing:.12em;text-transform:uppercase;margin-bottom:4px}.hero-card.learn .hero-kicker{color:#4338ca}.hero-card.quiz .hero-kicker{color:#b45309}.hero-card.exercise .hero-kicker{color:#0e7490}.hero-card.revision .hero-kicker{color:#7e22ce}.hero-card.pyqs .hero-kicker{color:#c2410c}.hero-card.tests .hero-kicker{color:#0369a1}.hero-row{display:flex;justify-content:space-between;align-items:center;gap:12px}.hero-card h2{margin:2px 0 4px;font-family:Roboto Slab,Roboto,serif;font-size:21px;letter-spacing:-.01em;font-weight:700;line-height:1.25}.hero-card p{margin:0;color:var(--ink-light);font-size:13px;line-height:1.55;max-width:600px}.hero-badge{min-width:58px;height:58px;border-radius:14px;background:#fffffff0;backdrop-filter:blur(6px);border:1px solid rgba(255,255,255,.7);display:flex;flex-direction:column;align-items:center;justify-content:center;box-shadow:var(--shadow-sm);flex-shrink:0}.hero-badge b{font-size:20px;line-height:1}.hero-badge small{font-size:7.5px;font-weight:800;letter-spacing:.06em;color:var(--muted);margin-top:2px}.chapter-nav{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:14px;margin-bottom:20px;box-shadow:var(--shadow-sm)}.chapter-nav-title{font-size:9.5px;font-weight:800;letter-spacing:.1em;color:var(--muted);text-transform:uppercase;margin-bottom:8px}.chapter-nav-grid{display:grid;grid-template-columns:1fr;gap:6px}@media(min-width:500px){.chapter-nav-grid{grid-template-columns:repeat(2,1fr)}}@media(min-width:760px){.chapter-nav-grid{grid-template-columns:repeat(3,1fr)}}.nav-pill{display:flex;align-items:center;gap:8px;padding:8px 10px;background:var(--surface-2);border:1px solid var(--line);border-radius:var(--radius-sm);text-decoration:none;color:var(--ink);font-size:11.5px;font-weight:600;transition:all .15s ease}.nav-pill:hover{background:#fff;border-color:var(--learn);transform:translateY(-1px)}.nav-pill b{color:var(--learn);font-family:JetBrains Mono,monospace;font-size:10.5px}.ncert-section{scroll-margin-top:16px;margin-top:28px}.section-header{display:flex;align-items:center;gap:10px;padding-bottom:10px;border-bottom:2px solid var(--line);margin-bottom:14px}.section-num-badge{background:linear-gradient(135deg,#1e1b4b,#312e81);color:#fff;font-family:JetBrains Mono,monospace;font-weight:700;font-size:12px;padding:5px 9px;border-radius:8px;letter-spacing:.02em}.section-header h2{margin:0;font-family:Roboto Slab,Roboto,serif;font-size:19px;font-weight:700;letter-spacing:-.01em;color:var(--ink);line-height:1.25}.section-header span{display:block;font-size:8.5px;font-weight:800;letter-spacing:.1em;color:var(--muted);text-transform:uppercase}.concept-card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:16px 14px;margin:14px 0;box-shadow:var(--shadow-sm);position:relative;transition:border-color .2s ease}.concept-card.accent-indigo{border-left:4px solid #4f46e5}.concept-card.accent-amber{border-left:4px solid #f59e0b}.concept-card.accent-cyan{border-left:4px solid #0891b2}.concept-card.accent-purple{border-left:4px solid #9333ea}.concept-card.accent-rose{border-left:4px solid #e11d48}.concept-card.accent-teal{border-left:4px solid #0d9488}.concept-card.accent-blue{border-left:4px solid #2563eb}.concept-card.accent-emerald{border-left:4px solid #059669}.concept-tag{font-size:8.5px;font-weight:800;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);margin-bottom:3px;display:inline-block}.concept-card h3{margin:0 0 8px;font-family:Roboto Slab,Roboto,serif;font-size:16.5px;font-weight:700;letter-spacing:-.01em;color:var(--ink);line-height:1.35}.concept-card h4{font-family:Roboto Slab,Roboto,serif;font-size:14px;margin:12px 0 5px;font-weight:600;color:var(--ink)}.concept-card p{margin:6px 0;font-size:13.5px;color:var(--ink-light);line-height:1.65}.concept-card ul,.concept-card ol{margin:6px 0 10px;padding-left:20px;font-size:13.5px;color:var(--ink-light);line-height:1.6}.concept-card li{margin:5px 0}.math-box{background:linear-gradient(135deg,#f8fafd,#f1f5fb);border:1px solid #c7d2fe;border-left:4px solid var(--learn);border-radius:var(--radius-sm);padding:12px 16px;margin:12px 0;font-size:15.5px;line-height:1.7;color:#0b1329;overflow-x:auto;box-shadow:0 1px 2px #0b132908}.math-box b,.math-box strong{font-weight:700;color:#312e81}.katex-display{margin:.5em 0!important}.katex{font-size:1.08em!important;text-rendering:auto}.formula-pill{display:inline-block;background:#eef2f8;border:1px solid #cbd5e1;padding:1px 6px;border-radius:5px;font-family:JetBrains Mono,monospace;font-size:11px;color:#0f172a;font-weight:600}.callout{border-radius:var(--radius-sm);padding:10px 12px;margin:10px 0;font-size:12px;line-height:1.5;display:block}.callout-info{background:#eef2ff;border-left:3px solid #4f46e5;color:#3730a3}.callout-tip{background:#ecfeff;border-left:3px solid #0891b2;color:#155e75}.callout-warn{background:#fffbeb;border-left:3px solid #f59e0b;color:#92400e}.table-container{margin:12px 0;overflow-x:auto;border-radius:var(--radius-sm);border:1px solid var(--line);background:#fff;box-shadow:var(--shadow-sm);-webkit-overflow-scrolling:touch}table{width:100%;border-collapse:collapse;font-size:12px;text-align:left;min-width:320px}th{background:#f6f8fc;color:#334155;font-weight:700;padding:8px 10px;border-bottom:2px solid var(--line);white-space:nowrap}td{padding:8px 10px;border-bottom:1px solid var(--line);vertical-align:top;color:#334155;line-height:1.45}tr:last-child td{border-bottom:none}tr:nth-child(2n){background:#fafcff}.td-mono{font-family:JetBrains Mono,monospace;font-size:11.5px;font-weight:600;color:#4f46e5;white-space:nowrap}.td-def{font-size:11px;color:#475569;line-height:1.45}.diagram-wrap{background:#f8fafd;border:1px solid var(--line);border-radius:var(--radius-sm);padding:12px;margin:12px 0;text-align:center;overflow:hidden}.diagram-caption{font-size:10.5px;font-weight:600;color:var(--muted);margin-top:6px}svg{width:100%;max-width:100%;height:auto;display:block;margin:0 auto}.solved-example{background:linear-gradient(135deg,#fff,#faf5ff);border:1.5px solid #e9d5ff;border-radius:var(--radius);padding:14px;margin:16px 0;box-shadow:var(--shadow-sm)}.example-header{display:flex;justify-content:space-between;align-items:center;gap:8px;margin-bottom:6px;flex-wrap:wrap}.example-badge{background:#9333ea;color:#fff;font-size:9.5px;font-weight:800;padding:2px 8px;border-radius:99px;letter-spacing:.04em;text-transform:uppercase}.example-title{font-family:Roboto Slab,Roboto,serif;font-size:14.5px;font-weight:700;color:#6b21a8;margin:0}.example-question{font-family:Roboto,sans-serif;font-size:14px;line-height:1.65;color:#1c1917;margin:6px 0 10px;font-weight:400}.example-solution-box{display:none;background:#fff;border:1px solid #e9d5ff;border-radius:var(--radius-sm);padding:14px;margin-top:10px;font-size:13px;line-height:1.65;color:#1e293b}.example-solution-box.open{display:block}.step-item{margin:6px 0;padding-left:10px;border-left:2px solid #d8b4fe}.step-item b{color:#7e22ce}.sol-toggle-btn{width:100%;display:flex;align-items:center;justify-content:space-between;background:#f1f5f9;border:1px solid #cbd5e1;color:#334155;border-radius:var(--radius-sm);padding:9px 12px;font-size:11.5px;font-weight:700;min-height:42px;transition:all .15s ease}.sol-toggle-btn:hover{background:#e2e8f0}.sol-toggle-btn.active{background:#0891b2;color:#fff;border-color:#0891b2}.sol-toggle-btn.pyq-btn.active{background:#ea580c;color:#fff;border-color:#ea580c}.sol-toggle-btn.example-btn.active{background:#9333ea;color:#fff;border-color:#9333ea}.exercise-card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);margin:14px 0;overflow:hidden;box-shadow:var(--shadow-sm)}.ex-top{padding:12px 14px;background:#f6f8fc;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between}.ex-badge{background:#0891b2;color:#fff;font-family:JetBrains Mono,monospace;font-weight:700;font-size:11px;padding:3px 8px;border-radius:6px}.ex-tag{font-size:9px;font-weight:800;letter-spacing:.08em;color:#0891b2;text-transform:uppercase}.ex-body{padding:14px}.ex-question{font-family:Roboto,sans-serif;font-size:14.5px;line-height:1.65;color:#0f172a;margin:0 0 12px;font-weight:400}.ex-subparts{display:grid;gap:8px;margin:10px 0}.ex-subpart{display:grid;grid-template-columns:26px 1fr;gap:8px;background:#f8fafd;border:1px solid var(--line);border-radius:var(--radius-sm);padding:8px 10px;font-family:Roboto,sans-serif;font-size:13.5px;line-height:1.55}.subpart-tag{font-family:JetBrains Mono,monospace;font-weight:700;font-size:11px;color:#0e7490;display:grid;place-items:center;background:#cffafe;height:22px;width:22px;border-radius:5px}.ex-prereq{display:flex;align-items:center;gap:6px;background:#ecfeff;border:1px solid #a5f3fc;border-radius:6px;padding:6px 10px;font-size:10.5px;margin-bottom:10px;flex-wrap:wrap}.ex-prereq span{color:#155e75;font-weight:700;text-transform:uppercase;letter-spacing:.04em}.ex-prereq a{color:#0891b2;font-weight:700;text-decoration:none}.ex-prereq a:hover{text-decoration:underline}.ex-solution-content{display:none;padding:12px;background:#fcfdfe;border:1px solid #a5f3fc;border-radius:var(--radius-sm);margin-top:10px;font-size:12.5px;line-height:1.55}.ex-solution-content.open{display:block}.final-ans-box{background:#ecfeff;border-left:3px solid #0891b2;padding:8px 12px;border-radius:0 var(--radius-sm) var(--radius-sm) 0;margin-bottom:10px;font-weight:600;font-size:12px;color:#155e75}.quiz-meta-bar{display:flex;justify-content:space-between;align-items:center;background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:10px 14px;margin-bottom:14px;box-shadow:var(--shadow-sm);font-size:12px}.filter-chips{display:flex;gap:6px;overflow-x:auto;padding-bottom:4px;margin-bottom:14px;-webkit-overflow-scrolling:touch}.chip{white-space:nowrap;background:#fff;border:1px solid var(--line);border-radius:99px;padding:5px 12px;font-size:10.5px;font-weight:700;color:var(--muted);transition:all .15s ease}.chip:hover{border-color:var(--line-strong);color:var(--ink)}.chip.active{background:var(--ink);color:#fff;border-color:var(--ink)}.mcq-card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:16px 14px;margin-bottom:14px;box-shadow:var(--shadow-sm)}.mcq-head{display:flex;justify-content:space-between;align-items:center;margin-bottom:8px}.mcq-num{background:#eef2f8;color:#3730a3;font-family:JetBrains Mono,monospace;font-size:10.5px;font-weight:700;padding:2px 7px;border-radius:5px}.mcq-status{font-size:9px;font-weight:800;letter-spacing:.06em;color:var(--muted);text-transform:uppercase}.mcq-question{font-size:14px;font-weight:600;line-height:1.45;margin:0 0 12px;color:var(--ink)}.mcq-options-stack{display:grid;gap:8px}.mcq-option-wrapper{display:flex;flex-direction:column;gap:4px}.mcq-option-btn{width:100%;display:flex;align-items:center;gap:10px;background:#f8fafd;border:1.5px solid var(--line);border-radius:var(--radius-sm);padding:9px 12px;text-align:left;font-size:12.5px;color:var(--ink-light);min-height:44px;transition:all .15s ease}.mcq-option-btn:hover:not(:disabled){background:#fff;border-color:var(--learn)}.opt-letter{font-family:JetBrains Mono,monospace;font-weight:700;font-size:10.5px;background:#e2e8f4;color:#475569;width:22px;height:22px;border-radius:5px;display:grid;place-items:center;flex-shrink:0}.mcq-option-btn.selected{border-color:var(--learn);background:#eef2ff}.mcq-option-btn.correct{border-color:#059669;background:#ecfdf5;color:#065f46;font-weight:600}.mcq-option-btn.correct .opt-letter{background:#059669;color:#fff}.mcq-option-btn.wrong{border-color:#e11d48;background:#fff1f2;color:#9f1239}.mcq-option-btn.wrong .opt-letter{background:#e11d48;color:#fff}.opt-explanation{display:none;padding:8px 10px;border-radius:6px;font-size:11.5px;line-height:1.45;animation:fadeIn .2s ease forwards}@keyframes fadeIn{0%{opacity:0;transform:translateY(-2px)}to{opacity:1;transform:translateY(0)}}.opt-explanation.show{display:block}.opt-explanation.correct-exp{background:#f0fdf4;border:1px solid #bbf7d0;color:#166534}.opt-explanation.wrong-exp{background:#f8fafd;border:1px solid #e2e8f0;color:#475569}.opt-explanation strong{font-weight:700;display:inline-block;margin-right:4px}.mcq-takeaway{display:none;margin-top:12px;padding:10px 12px;border-radius:var(--radius-sm);background:linear-gradient(135deg,#eef2ff,#f8fafd);border:1px solid #c7d2fe;font-size:12px;color:#3730a3;line-height:1.5}.mcq-takeaway.show{display:block}.mcq-takeaway-title{font-weight:800;font-size:10px;letter-spacing:.08em;text-transform:uppercase;color:#4338ca;margin-bottom:3px}.rev-grid{display:grid;grid-template-columns:1fr;gap:10px;margin:14px 0}@media(min-width:600px){.rev-grid{grid-template-columns:repeat(2,1fr)}}.rev-card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:14px 16px;box-shadow:var(--shadow-sm)}.rev-card h4{margin:0 0 4px;font-size:13.5px;font-weight:700;color:var(--revision)}.rev-card p{margin:0;font-size:12px;color:var(--ink-light);line-height:1.5}.mnemonic-badge{display:inline-block;background:#faf5ff;color:#7e22ce;border:1px solid #e9d5ff;padding:2px 7px;border-radius:5px;font-family:JetBrains Mono,monospace;font-size:10.5px;font-weight:700;margin:4px 0}.test-tab-btns{display:grid;grid-template-columns:repeat(3,1fr);gap:6px;margin-bottom:14px}.test-tab-btn{background:#fff;border:1px solid var(--line);border-radius:var(--radius-sm);padding:8px 4px;font-size:11px;font-weight:700;color:var(--muted);text-align:center;transition:all .15s ease}.test-tab-btn.active{background:var(--test);color:#fff;border-color:var(--test)}.test-card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:14px 12px;margin:10px 0;box-shadow:var(--shadow-sm)}.test-card-q{font-size:13px;font-weight:700;margin-bottom:10px}.test-actions-bar{position:sticky;bottom:calc(var(--nav-h) + 8px);background:#fffffff5;backdrop-filter:blur(10px);border:1px solid var(--line);border-radius:var(--radius);padding:10px 14px;display:flex;justify-content:space-between;align-items:center;box-shadow:var(--shadow-lg);margin-top:16px;z-index:10}.test-result-box{display:none;margin-top:14px;padding:14px;border-radius:var(--radius);background:#ecfeff;border:1px solid #a5f3fc;color:#0e7490;font-weight:700;font-size:13px;text-align:center}.test-result-box.show{display:block}.page-footer{text-align:center;padding:24px 12px 8px;font-size:11px;color:var(--muted);border-top:1px solid var(--line);margin-top:30px}.nav-bar{position:fixed;bottom:0;left:0;right:0;height:var(--nav-h);background:#fffffff5;backdrop-filter:blur(16px);border-top:1px solid var(--line);display:flex;justify-content:center;z-index:100;box-shadow:0 -3px 15px #0000000a}.nav-inner{width:100%;max-width:880px;display:grid;grid-template-columns:repeat(6,1fr);height:100%;padding:0 4px}.nav-btn{background:transparent;border:none;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:3px;color:#64748b;font-size:10px;font-weight:700;transition:color .15s ease;position:relative}.nav-btn svg{width:20px;height:20px;margin:0}.nav-btn.active{font-weight:800}.nav-btn.active[data-tab=learn]{color:var(--learn)}.nav-btn.active[data-tab=quiz]{color:var(--quiz)}.nav-btn.active[data-tab=exercise]{color:var(--ncert)}.nav-btn.active[data-tab=revision]{color:var(--revision)}.nav-btn.active[data-tab=pyqs]{color:var(--pyq)}.nav-btn.active[data-tab=tests]{color:var(--test)}.nav-btn.active:after{content:"";position:absolute;top:0;left:20%;right:20%;height:3px;border-radius:0 0 3px 3px}.nav-btn.active[data-tab=learn]:after{background:var(--learn)}.nav-btn.active[data-tab=quiz]:after{background:var(--quiz)}.nav-btn.active[data-tab=exercise]:after{background:var(--ncert)}.nav-btn.active[data-tab=revision]:after{background:var(--revision)}.nav-btn.active[data-tab=pyqs]:after{background:var(--pyq)}.nav-btn.active[data-tab=tests]:after{background:var(--test)}@media(min-width:768px){.app{padding:0 24px}header{padding:28px 0 12px}h1{font-size:34px}.section-header h2{font-size:22px}}@media(max-width:600px){.ex-solution-content,.example-solution-box{border:none!important;background:transparent!important;padding:8px 0!important;border-radius:0!important;margin-left:0!important;margin-right:0!important}.step-item{background:transparent!important;padding-left:8px!important;padding-right:0!important;margin-left:0!important;margin-right:0!important;border-radius:0!important}}
