:root{--bg:#faf9fd;--surface:#fff;--ink:#252332;--muted:#777583;--line:#e9e6ee;--accent:#8052d9;--soft:#f4effd;--green:#22865d;--red:#c14a56;--shadow:0 8px 26px rgba(50,36,76,.045)}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font-family:Inter,-apple-system,BlinkMacSystemFont,"Segoe UI",Arial,sans-serif;line-height:1.45}button,input{font:inherit}button{cursor:pointer}.app{max-width:860px;margin:auto;min-height:100vh;padding-bottom:90px}.top{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:22px 22px 16px;background:var(--bg);position:sticky;top:0;z-index:9;border-bottom:1px solid var(--line)}.brand{display:flex;gap:11px;align-items:center}.logo{display:grid;place-items:center;width:42px;height:42px;border:1.5px solid #d8c9f7;color:var(--accent);font-size:29px;border-radius:13px;background:#fff}.brand-title{font-size:17px;font-weight:780;letter-spacing:-.4px}.brand-sub{font-size:12px;color:var(--muted)}a{color:var(--accent);text-decoration:none}.botlink{font-size:12px;font-weight:700;white-space:nowrap;border:1px solid var(--line);border-radius:11px;padding:9px 12px;background:white}main{padding:22px}.eyebrow{font-size:11px;font-weight:800;letter-spacing:.11em;color:var(--accent);text-transform:uppercase;margin-bottom:8px}.hero{background:white;border:1px solid var(--line);border-radius:22px;padding:23px;box-shadow:var(--shadow)}h1{font-size:clamp(25px,5vw,36px);line-height:1.12;letter-spacing:-1.1px;margin:0 0 12px}h2{font-size:21px;letter-spacing:-.6px;margin:28px 0 13px}h3{font-size:16px;margin:0 0 5px}.muted{color:var(--muted)}.small{font-size:13px}.hero p{margin:0 0 18px;color:var(--muted)}.row{display:flex;align-items:center;justify-content:space-between;gap:12px}.progress{height:8px;background:#eee9f5;border-radius:12px;overflow:hidden}.progress>i{display:block;height:100%;background:var(--accent);border-radius:12px;transition:width .3s}.stats{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin:16px 0}.stat{padding:15px;background:white;border:1px solid var(--line);border-radius:15px}.stat b{display:block;font-size:23px}.stat span{font-size:11px;color:var(--muted)}.button{border:0;border-radius:12px;background:var(--accent);color:white;padding:12px 17px;font-weight:750}.button.secondary{background:white;color:var(--ink);border:1px solid var(--line)}.button:disabled{opacity:.4;cursor:default}.search{width:100%;padding:14px 16px;border-radius:13px;border:1px solid var(--line);background:white;color:var(--ink);outline:0}.search:focus{border-color:var(--accent)}.chips{display:flex;gap:7px;overflow-x:auto;padding:12px 0 14px;scrollbar-width:none}.chip{border:1px solid var(--line);border-radius:99px;padding:8px 12px;background:white;white-space:nowrap;font-size:12px;color:var(--muted)}.chip.selected{color:var(--accent);border-color:#bca5ed;background:var(--soft);font-weight:750}.list{display:grid;gap:9px}.lesson,.situation{background:white;border:1px solid var(--line);border-radius:15px;padding:16px;display:flex;gap:12px;align-items:center;text-align:left;width:100%;color:var(--ink)}.lesson:hover,.situation:hover{border-color:#cbb8f3}.lesson-body{flex:1;min-width:0}.lesson p{font-size:12px;color:var(--muted);margin:4px 0 0}.meta{font-size:11px;color:var(--accent);font-weight:750;margin-bottom:4px}.arrow{font-size:20px;color:#b4a7c9}.check{color:var(--green)}.category-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:10px}.category{border:1px solid var(--line);border-radius:15px;padding:17px;background:white;text-align:left}.category b{display:block;font-size:14px}.category span{font-size:12px;color:var(--muted)}.category .symbol{font-size:23px;color:var(--accent);display:block;margin-bottom:10px}.notice{border:1px solid #e4d7fa;background:#fbf9ff;border-radius:14px;padding:14px 15px;font-size:13px;margin:17px 0}.notice strong{display:block;margin-bottom:4px}.breadcrumbs{border:0;background:none;padding:0;color:var(--accent);font-weight:700;margin-bottom:18px}.lesson-title{font-size:28px;letter-spacing:-.7px;margin:6px 0}.step{display:flex;gap:13px;margin:0 0 10px;padding:16px;background:white;border:1px solid var(--line);border-radius:14px}.step-number{flex:none;display:grid;place-items:center;width:27px;height:27px;background:var(--soft);color:var(--accent);font-weight:800;border-radius:9px;font-size:12px}.step p{margin:2px 0 0;font-size:14px}.lesson-actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:18px}.nav{position:fixed;bottom:0;left:50%;transform:translateX(-50%);width:min(860px,100%);display:grid;grid-template-columns:repeat(5,1fr);background:white;border-top:1px solid var(--line);padding:8px 7px max(8px,env(safe-area-inset-bottom));z-index:20}.nav button{background:none;border:0;color:#858090;font-size:10px;font-weight:650;display:flex;align-items:center;flex-direction:column;gap:2px;padding:3px 0}.nav button span{font-size:24px;line-height:25px}.nav button.active{color:var(--accent)}.quiz-card{padding:20px;background:white;border:1px solid var(--line);border-radius:18px}.option{display:block;width:100%;text-align:left;border:1px solid var(--line);background:white;border-radius:11px;padding:13px;margin:8px 0;color:var(--ink)}.option.selected{border-color:var(--accent);background:var(--soft)}.option.correct{border-color:var(--green);background:#f0fbf5}.option.wrong{border-color:var(--red);background:#fff3f4}.empty{text-align:center;padding:45px 20px;color:var(--muted)}.tag{font-size:11px;color:var(--accent);font-weight:700}.footer{font-size:12px;color:var(--muted);padding:24px 0;text-align:center}.seg{display:flex;gap:7px;margin:15px 0}.seg button{padding:8px 12px;background:white;border:1px solid var(--line);border-radius:10px;font-size:12px}.seg button.selected{background:var(--soft);border-color:#bca5ed;color:var(--accent)}@media(min-width:700px){.category-grid{grid-template-columns:repeat(3,1fr)}.top{padding-left:30px;padding-right:30px}main{padding:28px 30px}}@media(max-width:370px){.top{padding:13px}.brand-title{font-size:15px}.botlink{padding:8px;font-size:11px}main{padding:15px}.hero{padding:18px}}

.category-description{font-size:12px;color:#77748a;line-height:1.45;display:block;margin:4px 0 8px}.search-shortcut{display:block;width:100%;border:1px solid #dedbe9;background:#fff;border-radius:13px;padding:15px 17px;text-align:left;color:#77748a;font:inherit;cursor:pointer;margin:18px 0 24px}.search-shortcut:hover{border-color:#9479d4}.category-grid{grid-template-columns:repeat(2,minmax(0,1fr))}@media(max-width:420px){.category-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.category{padding:15px 12px}.category b{font-size:14px}}

.quiz-exit{display:inline-flex;align-items:center;margin:0 0 18px;padding:11px 15px;border:1px solid #ddd7ea;border-radius:12px;background:#fff;color:#382f50;font-weight:650;cursor:pointer}

button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid #9c7ae3;outline-offset:2px}.category{min-width:0;overflow-wrap:anywhere}.option:disabled{cursor:default;opacity:1}.nav button{min-height:43px}.notice{overflow-wrap:anywhere}@media(max-width:370px){.brand{gap:7px}.logo{width:35px;height:35px;font-size:24px}.brand-title{font-size:14px}.botlink{padding:7px;font-size:10px}}

.visuals{margin:24px 0}.visual-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,220px),1fr));gap:14px}.visual-grid figure{margin:0;padding:10px;border:1px solid #dedbe9;border-radius:14px;background:#fff}.visual-grid img{width:100%;height:230px;object-fit:contain;display:block;border-radius:9px;background:#f6f5fa}.visual-grid figcaption{font-size:12px;color:#626070;margin-top:9px;line-height:1.5}.visual-grid a{display:block;cursor:zoom-in}.visual-grid a:focus-visible{outline:3px solid #8052ce;outline-offset:3px}

/* Improved mobile navigation, accessible sticky return control */
.sticky-back{position:sticky;top:0;z-index:30;background:rgba(250,249,253,.97);backdrop-filter:blur(12px);padding:9px 0;margin:-6px 0 10px}.sticky-exit{position:sticky;top:0;z-index:30;box-shadow:0 3px 12px #31234a16}.hero-actions{display:flex;flex-wrap:wrap;gap:9px}.hero-actions .button{white-space:normal;text-align:center}.hero-actions button:disabled{opacity:.5;cursor:not-allowed}.inline-visual{margin:8px 0 18px 42px;padding:12px;border:1px solid #dedbe9;border-radius:14px;background:white}.inline-visual img{display:block;width:100%;max-height:360px;object-fit:contain;background:#f7f6fa;border-radius:9px}.inline-visual figcaption{font-size:12px;color:#656074;line-height:1.5;margin-top:8px}.inline-visual a{display:block;cursor:zoom-in}.nav{grid-template-columns:repeat(4,minmax(0,1fr))}.nav button{min-width:0}@media(max-width:420px){.hero-actions{flex-direction:column}.hero-actions .button{width:100%}.inline-visual{margin-left:0}}

.brand-image{width:104px;height:auto;max-height:52px;object-fit:contain;flex-shrink:0;display:block}.brand{min-width:0}.brand>div{min-width:0}.brand-title{font-size:15px}.sticky-back{top:74px;z-index:8}.sticky-exit{top:74px;z-index:8}@media(max-width:420px){.brand-image{width:79px;max-height:44px}.brand-title{font-size:13px}.brand-sub{font-size:11px}.top{gap:7px;padding:13px 10px}.botlink{font-size:10px;padding:7px}.sticky-back,.sticky-exit{top:61px}}

.home-search{margin:18px 0;padding:16px;border:1px solid #dedbe9;border-radius:15px;background:#fff}.home-search label{display:block;font-weight:700;margin-bottom:8px}.home-search .search{margin:0}.home-search #home-search-results{margin-top:10px}.home-search #home-search-results:empty{display:none}.home-search .list{max-height:430px;overflow-y:auto}

/* Final navigation and mobile usability pass */
.sticky-back,.sticky-exit{top:var(--header-height,78px)}.top{min-height:78px}.brand-image{object-fit:contain;object-position:center;width:min(104px,25vw);height:auto;max-height:none}.lesson-actions .button{min-height:44px}.step{align-items:flex-start}.step p{overflow-wrap:anywhere}.quiz-card h2{line-height:1.3}@media(max-width:420px){.top{min-height:65px}.sticky-back,.sticky-exit{top:65px}.brand-image{width:min(79px,23vw)}.lesson-actions .button{flex:1 1 100%}}

.app{padding-bottom:180px}

.sources-panel{margin:22px 0;padding:16px;border:1px solid #dedbe9;border-radius:14px;background:#fff;overflow-wrap:anywhere}.sources-panel h2{font-size:18px;margin:0 0 10px}.sources-panel p{margin:9px 0}.sources-panel small{color:#656074}.notice .sources-panel{font-size:14px}

/* Keep return controls below the measured, responsive header. */
.sticky-back,.sticky-exit{top:var(--header-height,78px)}