:root{color-scheme:light;--color-ink: #102a2a;--color-ink-soft: #375453;--color-muted: #667a78;--color-line: #d8e4e1;--color-surface: #ffffff;--color-page: #f5faf8;--color-band: #eef8f5;--color-accent: #117b63;--color-accent-strong: #0c614e;--color-accent-soft: #d7fff2;--color-warm: #ffb84d;--color-coral: #ff6b5a;--color-success: #12805c;--color-danger: #b8322a;--color-header: rgba(255, 255, 255, .92);--color-on-accent: #ffffff;--color-button-disabled: #9ab8b0;--color-ghost-disabled: #f1f5f4;--color-warning-bg: #fff1cf;--color-warning-ink: #735100;--color-code-inline-bg: #e8f2ef;--color-code-block-bg: #102a2a;--color-code-block-ink: #d7fff2;--color-subtle-surface: #fbfdfc;--color-progress-track: #e8f2ef;--color-mobile-nav-link: #f4faf8;--shadow-soft: 0 18px 45px rgba(16, 42, 42, .08);--max-width: 1120px}[data-theme=dark]{color-scheme:dark;--color-ink: #e8f4ef;--color-ink-soft: #bad0ca;--color-muted: #91aaa3;--color-line: #25413c;--color-surface: #101c1a;--color-page: #071312;--color-band: #0c1a17;--color-accent: #6ee7bd;--color-accent-strong: #9df3d7;--color-accent-soft: #173d34;--color-warm: #f5c76f;--color-coral: #ff8b7f;--color-success: #53d5a6;--color-danger: #ff8b7f;--color-header: rgba(7, 19, 18, .92);--color-on-accent: #06110f;--color-button-disabled: #325d51;--color-ghost-disabled: #132420;--color-warning-bg: #382a11;--color-warning-ink: #ffd88a;--color-code-inline-bg: #142c27;--color-code-block-bg: #05100f;--color-code-block-ink: #d9fff2;--color-subtle-surface: #0d1917;--color-progress-track: #20352f;--color-mobile-nav-link: #10221e;--shadow-soft: 0 18px 45px rgba(0, 0, 0, .36)}@media(prefers-reduced-motion:no-preference){.theme-is-changing,.theme-is-changing *,.theme-is-changing *:before,.theme-is-changing *:after{transition:background-color .24s ease,border-color .24s ease,box-shadow .24s ease,color .24s ease,fill .24s ease,stroke .24s ease}}*{box-sizing:border-box}html{min-width:320px;background:var(--color-page)}body{margin:0;color:var(--color-ink);background:var(--color-page);font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;font-size:17px;line-height:1.65}body,button,input{-webkit-font-smoothing:antialiased}img,svg{display:block;max-width:100%}a{color:inherit}button,input{font:inherit}button{cursor:pointer}button:disabled{cursor:not-allowed}.skip-link{position:absolute;top:.75rem;left:.75rem;z-index:20;transform:translateY(-160%);background:var(--color-ink);color:var(--color-page);padding:.55rem .75rem;border-radius:8px}.skip-link:focus{transform:translateY(0)}.site-header{position:sticky;top:0;z-index:10;background:var(--color-header);border-bottom:1px solid var(--color-line);backdrop-filter:blur(14px)}.site-header__inner{max-width:var(--max-width);margin:0 auto;padding:.85rem 1.25rem;display:flex;align-items:center;justify-content:space-between;gap:1rem}.brand{display:inline-flex;align-items:center;flex:0 0 auto;gap:.65rem;text-decoration:none;font-weight:800}.brand__mark{display:grid;place-items:center;width:2.25rem;height:2.25rem;border-radius:8px;background:var(--color-ink);color:var(--color-accent-soft);font-size:.85rem}.brand__text{white-space:nowrap}.nav-toggle{display:none;width:2.75rem;height:2.75rem;align-items:center;justify-content:center;flex:0 0 auto;flex-direction:column;gap:.28rem;padding:0;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);color:var(--color-ink)}.nav-toggle:hover{border-color:var(--color-accent)}.site-header__actions{order:3;display:flex;align-items:center;flex:0 0 auto;gap:.5rem}.theme-toggle{display:inline-grid;place-items:center;width:2.75rem;height:2.75rem;flex:0 0 auto;padding:0;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);color:var(--color-ink)}.theme-toggle:hover{border-color:var(--color-accent);color:var(--color-accent-strong)}.theme-toggle__icon{width:1.15rem;height:1.15rem;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round}.theme-toggle__icon--sun,[data-theme=dark] .theme-toggle__icon--moon{display:none}[data-theme=dark] .theme-toggle__icon--sun{display:block}.nav-toggle__bar{display:block;width:1.25rem;height:2px;border-radius:999px;background:currentColor;transition:transform .16s ease,opacity .16s ease}.site-header.is-menu-open .nav-toggle__bar:nth-child(1){transform:translateY(6px) rotate(45deg)}.site-header.is-menu-open .nav-toggle__bar:nth-child(2){opacity:0}.site-header.is-menu-open .nav-toggle__bar:nth-child(3){transform:translateY(-6px) rotate(-45deg)}.primary-nav,.footer-links{display:flex;align-items:center;flex-wrap:wrap;gap:.4rem}.primary-nav{order:2;justify-content:flex-end;margin-left:auto}.primary-nav__link,.footer-links a{padding:.45rem .65rem;border-radius:8px;color:var(--color-ink-soft);text-decoration:none;font-size:.95rem}.primary-nav__link:hover,.primary-nav__link.is-active,.footer-links a:hover{background:var(--color-accent-soft);color:var(--color-ink)}.section{max-width:var(--max-width);margin:0 auto;padding:4.5rem 1.25rem}.section--tight{padding-top:2.8rem}.section--muted{max-width:none;background:var(--color-band)}.section--muted>*{max-width:var(--max-width);margin-left:auto;margin-right:auto}.home-hero{min-height:620px;display:grid;grid-template-columns:minmax(0,.9fr) minmax(320px,1.1fr);align-items:center;gap:3rem}.home-hero__copy{max-width:560px}.home-hero h1,.page-intro h1,.topic-header h1,.quiz-page__intro h1{margin:0;font-size:3.2rem;line-height:1.04;overflow-wrap:anywhere}.home-hero p,.page-intro p,.topic-header p,.quiz-page__intro p{color:var(--color-ink-soft);font-size:1.1rem;max-width:720px}.home-hero__image{width:100%;border-radius:8px;box-shadow:var(--shadow-soft);border:1px solid var(--color-line);background:var(--color-surface)}.eyebrow{margin:0 0 .65rem;color:var(--color-accent-strong);font-size:.78rem;font-weight:800;letter-spacing:0;text-transform:uppercase}.button-row{display:flex;align-items:center;flex-wrap:wrap;gap:.75rem;margin-top:1.4rem}.button{display:inline-flex;align-items:center;justify-content:center;min-height:2.75rem;padding:.65rem 1rem;border:1px solid transparent;border-radius:8px;text-decoration:none;font-weight:800;line-height:1.2;text-align:center}.button--primary{background:var(--color-accent);color:var(--color-on-accent)}.button--primary:hover{background:var(--color-accent-strong)}.button--primary:disabled{background:var(--color-button-disabled)}.button--ghost{background:var(--color-surface);border-color:var(--color-line);color:var(--color-ink)}.button--ghost:hover{border-color:var(--color-accent)}.button--ghost:disabled{color:var(--color-muted);background:var(--color-ghost-disabled)}.section-heading{margin-bottom:1.5rem}.section-heading h2,.related-topics h2,.sidebar-block h2,.contact-panel h2{margin:0;font-size:1.75rem;line-height:1.2}.section-heading p{max-width:720px;color:var(--color-ink-soft)}.course-level-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,16rem),1fr));gap:1rem}.course-level-card{display:grid;align-content:start;gap:1rem;padding:1.25rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);box-shadow:var(--shadow-soft)}.course-level-card h3,.course-level-card p{margin:0}.course-level-card h3{font-size:1.45rem;line-height:1.2}.course-level-card p:not(.eyebrow){color:var(--color-ink-soft)}.course-level-card__meta,.course-level-card__actions{display:flex;align-items:center;flex-wrap:wrap;gap:.75rem}.course-level-card__meta{color:var(--color-muted);font-size:.92rem;font-weight:800}.course-level-card__meta span{padding:.22rem .55rem;border-radius:999px;background:var(--color-accent-soft);color:var(--color-accent-strong)}.course-level-card__actions{margin-top:.25rem}.progress-panel{max-width:var(--max-width);margin:1.25rem auto 2.5rem;padding:1.25rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);box-shadow:var(--shadow-soft)}.progress-panel__copy{display:grid;gap:.35rem}.progress-panel__copy h2,.progress-panel__copy p{margin:0}.progress-panel__copy p:not(.eyebrow){color:var(--color-ink-soft)}.progress-meter{height:.65rem;margin:1rem 0;overflow:hidden;border-radius:999px;background:var(--color-progress-track)}.progress-meter span{display:block;width:0;height:100%;border-radius:inherit;background:var(--color-accent);transition:width .22s ease}.progress-panel__stats{display:flex;align-items:center;flex-wrap:wrap;gap:.6rem}.progress-panel__stats span{padding:.3rem .65rem;border-radius:999px;background:var(--color-code-inline-bg);color:var(--color-ink-soft);font-size:.92rem;font-weight:800}.topic-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,19rem),1fr));gap:1rem}.topic-grid--featured{grid-template-columns:minmax(0,1fr);max-width:760px}.topic-card{min-height:220px;display:flex;flex-direction:column;justify-content:space-between;gap:1rem;padding:1.15rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);text-decoration:none}.topic-card--ready:hover{border-color:var(--color-accent);box-shadow:var(--shadow-soft);transform:translateY(-2px)}.topic-card--planned{opacity:.82}.topic-card__meta,.topic-card__footer,.review-item__header,.quiz-app__topline{display:flex;align-items:center;justify-content:space-between;gap:1rem}.topic-card__meta,.topic-card__footer{color:var(--color-muted);font-size:.88rem;font-weight:700}.topic-card h3{margin:0;font-size:1.25rem;overflow-wrap:anywhere}.topic-card p{margin:0;color:var(--color-ink-soft)}.status-pill{padding:.2rem .55rem;border-radius:999px;font-size:.8rem}.status-pill--ready{color:var(--color-accent-strong);background:var(--color-accent-soft)}.status-pill--planned{color:var(--color-warning-ink);background:var(--color-warning-bg)}.page-intro{padding-bottom:2rem}.subject-list,.contact-panel{display:grid;gap:1rem}.subject-row,.contact-panel{border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);padding:1.25rem}.contact-panel{margin-bottom:3rem}.subject-row{display:flex;align-items:center;justify-content:space-between;gap:1rem;text-decoration:none}.subject-row:hover{border-color:var(--color-accent)}.subject-row h2,.subject-row p{margin:0}.subject-row p,.muted{color:var(--color-muted)}.course-index{display:grid;gap:1rem}.lesson-group{border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);box-shadow:var(--shadow-soft);overflow:hidden}.lesson-group summary{display:flex;align-items:center;justify-content:space-between;gap:1rem;min-height:4.25rem;padding:1rem 1.15rem;cursor:pointer;list-style:none}.lesson-group summary::-webkit-details-marker{display:none}.lesson-group summary:after{content:"+";display:grid;place-items:center;width:1.75rem;height:1.75rem;flex:0 0 auto;border:1px solid var(--color-line);border-radius:8px;color:var(--color-accent-strong);font-size:1.2rem;font-weight:900;line-height:1}.lesson-group[open] summary:after{content:"-"}.lesson-group summary>span:first-child{display:grid;gap:.25rem}.lesson-group summary strong{font-size:1.1rem}.lesson-group summary small,.lesson-row small{color:var(--color-muted)}.lesson-group summary>span:last-child{color:var(--color-accent-strong);font-size:.9rem;font-weight:900;white-space:nowrap}.lesson-list{display:grid;gap:0;margin:0;padding:0;list-style:none;border-top:1px solid var(--color-line)}.lesson-group__content{overflow:hidden}.lesson-row{display:grid;grid-template-columns:minmax(0,1fr) auto;align-items:stretch;border-bottom:1px solid var(--color-line)}.lesson-row:last-child{border-bottom:0}.lesson-row__main{display:grid;grid-template-columns:2.25rem minmax(0,1fr);gap:.85rem;padding:.9rem 1rem;text-decoration:none}.lesson-row__main:hover,.lesson-row__quiz:hover{background:var(--color-accent-soft)}.lesson-row.is-completed{background:color-mix(in srgb,var(--color-accent-soft) 28%,transparent)}.lesson-row.is-in-progress{background:color-mix(in srgb,var(--color-warning-bg) 32%,transparent)}.lesson-row.is-attempted{background:color-mix(in srgb,var(--color-code-inline-bg) 40%,transparent)}.lesson-row__order{display:grid;place-items:center;width:2.25rem;height:2.25rem;border-radius:8px;background:var(--color-code-inline-bg);color:var(--color-accent-strong);font-size:.85rem;font-weight:900}.lesson-row.is-completed .lesson-row__order{background:var(--color-accent-soft)}.lesson-row.is-in-progress .lesson-row__order{background:var(--color-warning-bg);color:var(--color-warning-ink)}.lesson-row__main span:last-child{display:grid;gap:.15rem;min-width:0}.lesson-row__main strong,.lesson-row small{overflow-wrap:anywhere}.lesson-row__status{width:fit-content;margin-top:.15rem;padding:.14rem .48rem;border-radius:999px;background:var(--color-code-inline-bg);color:var(--color-muted)!important;font-size:.78rem;font-weight:900}.lesson-row.is-completed .lesson-row__status{background:var(--color-accent-soft);color:var(--color-accent-strong)!important}.lesson-row.is-in-progress .lesson-row__status{background:var(--color-warning-bg);color:var(--color-warning-ink)!important}.lesson-row.is-attempted .lesson-row__status{color:var(--color-ink-soft)!important}.lesson-row__quiz{display:inline-flex;align-items:center;justify-content:center;min-width:6rem;padding:.9rem 1rem;border-left:1px solid var(--color-line);color:var(--color-accent-strong);font-weight:900;text-decoration:none}.topic-article{max-width:var(--max-width);margin:0 auto;padding:3.5rem 1.25rem 4.5rem}.topic-header{max-width:820px;margin-bottom:2.5rem}.topic-header__actions{display:flex;align-items:center;flex-wrap:wrap;gap:.75rem;margin-top:1.35rem}.content-grid{display:grid;grid-template-columns:minmax(0,1fr) 280px;align-items:start;gap:2rem}.prose{max-width:760px;min-width:0}.prose--standalone{max-width:820px}.prose h2{margin-top:2.1rem;margin-bottom:.7rem;font-size:1.55rem;line-height:1.25}.prose p,.prose li{color:var(--color-ink-soft)}.prose a,.text-link{color:var(--color-accent-strong);font-weight:800}.prose code{padding:.12rem .28rem;border-radius:6px;background:var(--color-code-inline-bg);color:var(--color-ink)}.prose pre{overflow-x:auto;padding:1rem;border-radius:8px;background:var(--color-code-block-bg);color:var(--color-code-block-ink);-webkit-overflow-scrolling:touch}.prose pre code{padding:0;background:transparent;color:inherit}.study-sidebar{position:sticky;top:5.5rem}.sidebar-block{padding:1rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface)}.sidebar-block dl{display:grid;gap:.85rem;margin:1rem 0 0}.sidebar-block dl div{display:flex;align-items:center;justify-content:space-between;gap:1rem}.sidebar-block dt{color:var(--color-muted)}.sidebar-block dd{margin:0;font-weight:800}.related-topics{margin-top:3rem}.related-topics__grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:1rem;margin-top:1rem}.related-link{display:grid;gap:.35rem;min-height:104px;padding:1rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);text-decoration:none}.related-link:hover{border-color:var(--color-accent)}.related-link span{color:var(--color-muted);font-size:.88rem;font-weight:800}.related-link--muted{color:var(--color-muted)}.quiz-page{max-width:920px}.quiz-page__intro{margin-bottom:1.75rem}.quiz-app,.quiz-result,.quiz-empty{padding:1.25rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);box-shadow:var(--shadow-soft)}.quiz-app__topline{align-items:flex-start}.quiz-app h2,.quiz-app h3,.quiz-result h2,.review-item h3{margin:0;overflow-wrap:anywhere}.best-score{margin:0;padding:.35rem .6rem;border-radius:8px;background:var(--color-warning-bg);color:var(--color-warning-ink);font-weight:800;white-space:nowrap}.quiz-progress{height:.6rem;margin:1.25rem 0;overflow:hidden;border-radius:999px;background:var(--color-progress-track)}.quiz-progress span{display:block;height:100%;border-radius:inherit;background:var(--color-accent);transition:width .18s ease}.question-panel{padding-top:.5rem}.answer-options{display:grid;gap:.7rem;margin:1rem 0 0;padding:0;border:0}.answer-options legend{width:1px;height:1px;overflow:hidden;position:absolute;clip:rect(0 0 0 0)}.answer-option{display:flex;align-items:flex-start;gap:.75rem;min-height:3.25rem;padding:.85rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-subtle-surface)}.answer-option:hover{border-color:var(--color-accent)}.answer-option input{width:1.15rem;height:1.15rem;margin-top:.25rem;accent-color:var(--color-accent)}.answer-option span{overflow-wrap:anywhere}.quiz-controls{display:flex;justify-content:space-between;gap:1rem;margin-top:1.25rem}.quiz-controls__forward{display:flex;justify-content:flex-end;gap:.75rem}.quiz-app__status{margin:1rem 0 0;color:var(--color-muted);font-size:.95rem}.result-summary{padding-bottom:1.5rem;border-bottom:1px solid var(--color-line)}.result-summary__accuracy{margin:.35rem 0;color:var(--color-accent-strong);font-size:1.4rem;font-weight:900}.result-stats{display:flex;align-items:center;flex-wrap:wrap;gap:.6rem;margin:.9rem 0}.result-stats span{padding:.3rem .65rem;border-radius:999px;background:var(--color-code-inline-bg);color:var(--color-ink-soft);font-size:.92rem;font-weight:800}.review-list{display:grid;gap:1rem;margin-top:1.5rem}.review-item{padding:1rem;border:1px solid var(--color-line);border-left-width:5px;border-radius:8px;background:var(--color-subtle-surface)}.review-item.is-correct{border-left-color:var(--color-success)}.review-item.is-wrong{border-left-color:var(--color-danger)}.review-item.is-skipped{border-left-color:var(--color-warm)}.review-item.is-unanswered{border-left-color:var(--color-muted)}.review-item__header span{color:var(--color-muted);font-size:.9rem;font-weight:800}.review-item__explanation{color:var(--color-ink-soft);overflow-wrap:anywhere}.site-footer{border-top:1px solid var(--color-line);background:var(--color-surface)}.site-footer__inner{max-width:var(--max-width);margin:0 auto;padding:2rem 1.25rem;display:grid;grid-template-columns:1fr auto;align-items:start;gap:1rem}.site-footer__brand{margin:0;font-weight:900}.site-footer__copy{grid-column:1 / -1;margin:0;color:var(--color-muted);font-size:.92rem}.ad-slot{min-height:90px}@media(max-width:980px){.home-hero{min-height:auto;grid-template-columns:1fr;gap:2rem;padding-top:3rem}.home-hero__copy,.home-hero p{max-width:720px}.content-grid,.course-level-grid{grid-template-columns:1fr}.study-sidebar{position:static}}@media(max-width:860px){body{font-size:16px}.section{padding-top:3.25rem;padding-bottom:3.25rem}.site-header__inner{align-items:center;gap:.75rem;padding-top:.75rem;padding-bottom:.75rem;display:flex;position:relative}.nav-toggle{display:inline-flex}.primary-nav{position:absolute;top:calc(100% + .45rem);right:1.25rem;left:1.25rem;z-index:30;display:grid;grid-template-columns:1fr;gap:.35rem;width:auto;padding:.6rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);box-shadow:var(--shadow-soft);opacity:0;pointer-events:none;visibility:hidden;transform:translateY(-.4rem);transition:opacity .16s ease,visibility .16s ease,transform .16s ease}.site-header.is-menu-open .primary-nav{opacity:1;pointer-events:auto;visibility:visible;transform:translateY(0)}.primary-nav__link{min-height:2.45rem;display:inline-flex;align-items:center;justify-content:flex-start;padding:.6rem .7rem}.home-hero h1,.page-intro h1,.topic-header h1,.quiz-page__intro h1{font-size:2.35rem}.related-topics__grid{grid-template-columns:1fr}.site-footer__inner{display:flex;align-items:flex-start;flex-direction:column}.subject-row{align-items:flex-start;flex-direction:column}.lesson-group summary{align-items:flex-start}}@media(max-width:560px){.section,.topic-article,.progress-panel{padding-left:1rem;padding-right:1rem}.progress-panel{margin:.75rem 1rem 2rem}.site-header{position:sticky}.site-header__inner{padding-left:1rem;padding-right:1rem}.nav-toggle{width:2.6rem;height:2.6rem}.primary-nav__link{background:var(--color-mobile-nav-link)}.home-hero h1,.page-intro h1,.topic-header h1,.quiz-page__intro h1{font-size:2rem}.home-hero p,.page-intro p,.topic-header p,.quiz-page__intro p{font-size:1rem}.section-heading h2,.related-topics h2,.sidebar-block h2,.contact-panel h2{font-size:1.45rem}.home-hero__image{border-radius:6px}.topic-card{min-height:0;padding:1rem}.topic-card__meta,.topic-card__footer,.sidebar-block dl div{align-items:flex-start;flex-direction:column;gap:.35rem}.topic-header__actions{align-items:stretch;flex-direction:column}.quiz-page{padding-left:.85rem;padding-right:.85rem}.quiz-app,.quiz-result,.quiz-empty,.contact-panel{padding:1rem}.answer-option{padding:.8rem}.button,.quiz-controls .button,.course-level-card__actions .button{width:100%}.lesson-group summary{grid-template-columns:1fr}.lesson-group summary{display:grid}.lesson-group summary>span:last-child{white-space:normal}.lesson-row{grid-template-columns:1fr;gap:.75rem;padding:.95rem}.lesson-row__main{grid-template-columns:2rem minmax(0,1fr);gap:.75rem;padding:0}.lesson-row__order{width:2rem;height:2rem}.lesson-row__quiz{justify-self:start;min-width:0;min-height:2.35rem;margin-left:2.75rem;padding:.45rem .8rem;border:1px solid var(--color-line);border-radius:8px;background:var(--color-surface);justify-content:center}.quiz-controls,.quiz-controls__forward,.button-row,.quiz-app__topline,.review-item__header{align-items:stretch;flex-direction:column}.best-score{width:fit-content}}@media(max-width:380px){.brand__mark{width:2rem;height:2rem}.brand__text{font-size:.95rem}.primary-nav{right:1rem;left:1rem}.home-hero h1,.page-intro h1,.topic-header h1,.quiz-page__intro h1{font-size:1.8rem}.quiz-app,.quiz-result,.quiz-empty{padding:.85rem}}