:root{--primary: #004E92;--primary-dark: #000428;--accent: #FFD700;--text-main: #2d3436;--text-muted: #636e72;--bg-body: #f0f2f5;--bg-card: #ffffff;--header-h: 70px;--sidebar-w: 280px;--radius: 12px;--shadow-sm: 0 2px 4px rgba(0,0,0,.05);--shadow-lg: 0 15px 30px rgba(0,0,0,.1);--transition: all .3s cubic-bezier(.25, .8, .25, 1)}*{box-sizing:border-box;margin:0;padding:0;font-family:Segoe UI,system-ui,-apple-system,sans-serif}body{background-color:var(--bg-body);color:var(--text-main);line-height:1.6;padding-top:var(--header-h);padding-bottom:80px}.main-header{position:fixed;top:0;left:0;width:100%;height:var(--header-h);background:linear-gradient(135deg,var(--primary),var(--primary-dark));color:#fff;display:flex;justify-content:space-between;align-items:center;padding:0 2rem;z-index:1000;box-shadow:var(--shadow-sm)}.logo{font-weight:900;font-size:1.2rem;text-transform:uppercase;letter-spacing:1px;color:#fff;text-decoration:none;display:flex;align-items:center;gap:10px}.nav-desktop{display:flex;gap:25px}.nav-link{color:#ffffffb3;text-decoration:none;font-weight:600;position:relative;transition:var(--transition)}.nav-link:after{content:"";position:absolute;width:0%;height:2px;bottom:-5px;left:0;background-color:var(--accent);transition:var(--transition)}.nav-link:hover,.nav-link.active{color:#fff}.nav-link:hover:after,.nav-link.active:after{width:100%}.layout-wrapper{max-width:1200px;margin:40px auto;display:flex;gap:40px;padding:0 20px}.sidebar{width:var(--sidebar-w);min-width:var(--sidebar-w);height:calc(100vh - 120px);position:sticky;top:100px;background:var(--bg-card);border-radius:var(--radius);padding:25px;box-shadow:var(--shadow-sm);overflow-y:auto}.content-area{flex:1;min-width:0}.sidebar h3{font-size:.75rem;text-transform:uppercase;color:var(--text-muted);margin:20px 0 10px;letter-spacing:1.5px}.lang-btn{width:100%;display:flex;align-items:center;gap:12px;padding:14px 16px;margin-bottom:8px;border:none;background:transparent;color:var(--text-main);font-weight:600;border-radius:8px;cursor:pointer;transition:var(--transition);text-align:left}.lang-btn:hover{background-color:#f1f5f9;transform:translate(5px);color:var(--primary)}.lang-btn.active{background:linear-gradient(90deg,var(--primary),#0066cc);color:#fff;box-shadow:0 4px 12px #004e924d}.lang-section{display:none;animation:slideIn .4s ease-out}.lang-section.active{display:block}@keyframes slideIn{0%{opacity:0;transform:translateY(20px)}to{opacity:1;transform:translateY(0)}}.section-title{font-size:2rem;margin-bottom:30px;color:var(--primary-dark);display:flex;align-items:center;gap:15px}.code-card{background:var(--bg-card);border-radius:var(--radius);box-shadow:var(--shadow-lg);overflow:hidden;margin-bottom:30px;border:1px solid rgba(0,0,0,.05);transition:transform .3s ease}.code-card:hover{transform:translateY(-5px)}.card-header{background:#f8fafc;padding:15px 25px;border-bottom:1px solid #e2e8f0;font-weight:700;color:var(--text-muted);display:flex;justify-content:space-between;align-items:center}.badge-pro{background-color:var(--accent);color:var(--primary-dark);font-size:.7rem;padding:4px 8px;border-radius:4px;font-weight:800;text-transform:uppercase}.tip-box{background-color:#e0f2fe;border-left:5px solid var(--primary);padding:20px;border-radius:6px;margin-bottom:30px;display:flex;gap:20px;align-items:start;color:#0c4a6e}.tip-box i{font-size:1.5rem}.css-concept{background:#fff;border-radius:var(--radius);padding:25px;margin-bottom:30px;box-shadow:var(--shadow-sm);border-left:4px solid var(--primary)}.css-concept h3{color:var(--primary);margin-bottom:15px;display:flex;align-items:center;gap:10px}.css-concept p{margin-bottom:15px}.css-demo{background:#f8f9fa;border-radius:8px;padding:20px;margin:15px 0;border:1px solid #e9ecef}.demo-box{width:100px;height:100px;background:var(--primary);margin:10px auto;display:flex;align-items:center;justify-content:center;color:#fff;font-weight:700;border-radius:8px}.demo-flex{display:flex;gap:10px;margin:15px 0}.demo-flex-item{flex:1;background:var(--primary);padding:15px;border-radius:6px;color:#fff;text-align:center}.css-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin:15px 0}.grid-item{background:var(--primary);padding:15px;border-radius:6px;color:#fff;text-align:center}.property-table{width:100%;border-collapse:collapse;margin:20px 0}.property-table th,.property-table td{padding:12px 15px;text-align:left;border-bottom:1px solid #e2e8f0}.property-table th{background-color:#f8fafc;color:var(--primary);font-weight:600}.property-table tr:hover{background-color:#f8f9fa}.exercise{background:#fff9db;border-left:4px solid #ffd43b;padding:20px;border-radius:6px;margin:25px 0}.exercise h4{color:#e67700;margin-bottom:10px;display:flex;align-items:center;gap:10px}.menu-toggle,.mobile-menu,.mobile-lang-nav,.bottom-nav{display:none}@media (max-width: 768px){.layout-wrapper{flex-direction:column;padding:0 15px;margin-top:10px}.sidebar,.nav-desktop{display:none}.menu-toggle{display:block;font-size:1.5rem;cursor:pointer}.mobile-menu{display:block;position:fixed;top:var(--header-h);left:0;width:100%;background:#fff;padding:20px;box-shadow:0 10px 20px #0000001a;transform:translateY(-150%);transition:transform .4s cubic-bezier(.4,0,.2,1);z-index:99}.mobile-menu.open{transform:translateY(0)}.mobile-link{display:block;padding:15px;border-bottom:1px solid #f0f0f0;text-decoration:none;color:var(--text-main);font-weight:600}.mobile-lang-nav{display:flex;overflow-x:auto;gap:10px;padding:15px;background:#fff;position:sticky;top:var(--header-h);z-index:90;box-shadow:0 4px 10px #0000000d;scrollbar-width:none}.mobile-lang-nav::-webkit-scrollbar{display:none}.mob-pill{white-space:nowrap;padding:8px 16px;background:#f1f2f6;border-radius:20px;font-size:.9rem;font-weight:600;color:var(--text-muted);transition:.2s}.mob-pill.active{background:var(--primary);color:#fff}.bottom-nav{display:flex;position:fixed;bottom:0;left:0;width:100%;background:#fff;border-top:1px solid #eee;justify-content:space-around;padding:10px 0;z-index:1000}.bottom-item{display:flex;flex-direction:column;align-items:center;text-decoration:none;font-size:.7rem;color:#b2bec3}.bottom-item i{font-size:1.2rem;margin-bottom:4px}.bottom-item.active{color:var(--primary)}.demo-flex{flex-direction:column}.css-grid{grid-template-columns:1fr}}