.page-container{background-color:var(--bg-secondary);min-height:100vh;color:var(--text-primary);padding-bottom:4rem;font-family:Inter,system-ui,-apple-system,sans-serif}.hero-content{text-align:center;max-width:800px;margin:0 auto}.tabs-dock-container{z-index:50;justify-content:center;margin-bottom:2.5rem;display:flex;position:sticky;top:1rem}.glass-dock{background:var(--bg-overlay);-webkit-backdrop-filter:blur(12px);border:1px solid var(--border-primary);border-radius:9999px;gap:.5rem;padding:.5rem;display:flex;box-shadow:0 10px 15px -3px #0000001a}.tab-btn{color:var(--text-secondary);cursor:pointer;background:0 0;border:none;border-radius:9999px;align-items:center;gap:.5rem;padding:.75rem 1.5rem;font-size:.95rem;font-weight:600;transition:all .2s;display:flex}.tab-btn:hover{background-color:var(--surface-hover);color:var(--text-primary)}.tab-btn.active{background-color:var(--color-primary-600);color:#fff;box-shadow:0 2px 10px #04aa6d4d}.content-wrapper{max-width:840px;margin:0 auto;padding:0 1.5rem}.concept-card{background:var(--bg-primary);border:1px solid var(--border-primary);border-radius:1.5rem;padding:2.5rem;box-shadow:0 1px 2px #0000000d}.theory-item{background:0 0;border:none;margin-bottom:2rem;padding:0}.theory-item h4,h3,h2,h1{color:var(--text-primary);letter-spacing:-.01em;margin-bottom:1.25rem;font-weight:700}.theory-item h4{font-size:1.5rem}.theory-item h3{font-size:1.75rem}.theory-item h2{border-bottom:2px solid var(--border-secondary);margin-top:2rem;padding-bottom:.5rem;font-size:2rem}.theory-item h1{color:var(--color-primary-600);text-align:center;margin-bottom:2rem;font-size:2.5rem}.theory-item p,.theory-item li{color:var(--text-secondary);margin-bottom:1rem;font-size:1.125rem;line-height:1.8}.theory-item ul,.theory-item ol{margin-bottom:1.5rem;margin-left:1.5rem}.theory-item strong{color:var(--text-primary);font-weight:700}.formula-box{background-color:var(--bg-secondary);border-left:4px solid var(--color-primary-500);color:var(--text-primary);border-radius:0 .75rem .75rem 0;margin:1.5rem 0;padding:1.5rem;font-family:Fira Code,monospace;font-weight:500}.question-card-modern{background:var(--bg-primary);border:1px solid var(--border-primary);border-radius:1.5rem;margin-bottom:2.5rem;padding:2.5rem;transition:transform .3s cubic-bezier(.34,1.56,.64,1),box-shadow .3s;position:relative;overflow:visible;box-shadow:0 10px 15px -3px #0000001a}.question-card-modern:hover{transform:translateY(-4px);box-shadow:0 25px 50px -12px #0000001f}.q-header{border-bottom:1px solid var(--border-primary);justify-content:space-between;align-items:center;margin-bottom:2rem;padding-bottom:1.5rem;display:flex}.q-id{background:var(--bg-secondary);color:var(--text-tertiary);letter-spacing:.05em;border-radius:.75rem;padding:.5rem 1rem;font-family:monospace;font-size:.85rem;font-weight:700}.q-text{color:var(--text-primary);letter-spacing:-.015em;margin-bottom:2.5rem;font-family:Inter,system-ui,sans-serif;font-size:1.35rem;font-weight:600;line-height:1.7}.q-options-grid{grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:1.5rem;margin-bottom:2rem;display:grid}.q-option{background:var(--bg-secondary);cursor:pointer;border:2px solid #0000;border-radius:1rem;align-items:center;padding:1rem;transition:all .2s cubic-bezier(.4,0,.2,1);display:flex;position:relative}.q-option:hover{background:var(--bg-primary);border-color:var(--color-primary-500);transform:translateY(-2px);box-shadow:0 4px 6px -1px #0000001a}.q-option.correct{background-color:#dcfce7;border-color:#22c55e}.q-option.wrong{background-color:#fee2e2;border-color:#ef4444}.opt-label{background:var(--bg-tertiary);width:2.5rem;height:2.5rem;color:var(--text-secondary);border-radius:.75rem;flex-shrink:0;justify-content:center;align-items:center;margin-right:1rem;font-weight:700;transition:all .2s;display:flex}.q-option:hover .opt-label{background:var(--color-primary-600);color:#fff}details.group{border-top:2px dashed var(--border-primary);margin-top:2rem;padding-top:1.5rem}.solution-toggle{background:var(--bg-primary);border:2px solid var(--color-primary-100);width:100%;color:var(--color-primary-600);cursor:pointer;text-transform:uppercase;letter-spacing:.05em;-webkit-user-select:none;user-select:none;border-radius:1rem;justify-content:space-between;align-items:center;padding:1rem 1.5rem;font-size:.95rem;font-weight:700;list-style:none;transition:all .3s cubic-bezier(.4,0,.2,1);display:flex}.solution-toggle::-webkit-details-marker{display:none}.solution-content{background:var(--bg-primary);border:2px solid var(--accent-success,var(--color-primary));border-top:none;border-bottom-right-radius:1rem;border-bottom-left-radius:1rem;padding:2rem;animation:.3s ease-out forwards slideDown;position:relative;overflow:hidden}@keyframes slideDown{0%{opacity:0;transform:translateY(-10px)}to{opacity:1;transform:translateY(0)}}.fade-in{animation:.4s ease-out forwards fadeIn}@keyframes fadeIn{0%{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}.lang-toggle-container{-webkit-backdrop-filter:blur(8px);backdrop-filter:blur(8px);background:#fff3;border-radius:.75rem;gap:.25rem;padding:.25rem;display:flex;position:absolute;top:2rem;right:2rem}.lang-btn{color:#fffc;cursor:pointer;background:0 0;border:none;border-radius:.5rem;padding:.5rem 1rem;font-size:.875rem;font-weight:600;transition:all .2s}.lang-btn:hover{color:#fff;background:#ffffff1a}.lang-btn.active{color:var(--color-primary-600);background:#fff;box-shadow:0 2px 4px #0000001a}.frac{color:var(--color-primary-600);background:var(--color-primary-100);border:1px solid var(--border-primary);border-radius:6px;padding:0 6px;font-family:Fira Code,monospace;font-size:1.1em;font-weight:800;display:inline-block;transform:translateY(-1px)}.math-exp{color:var(--color-primary-600);background:var(--color-primary-100);border:1px solid var(--border-primary);border-radius:6px;margin:0 4px;padding:2px 8px;font-family:Fira Code,monospace;font-size:1.05em;font-weight:700;display:inline-block;box-shadow:0 1px 2px #0000000d}.v-frac{vertical-align:middle;color:var(--color-primary-600);background:var(--color-primary-50);border:1px solid var(--color-primary-100);border-radius:6px;flex-direction:column;align-items:center;margin:0 4px;padding:4px 6px;font-family:Fira Code,monospace;font-weight:700;display:inline-flex;transform:translateY(2px)}.v-frac .num{text-align:center;border-bottom:2px solid;width:100%;padding:0 4px;font-size:.9em}.v-frac .den{text-align:center;width:100%;padding:0 4px;font-size:.9em}.root{border-top:2px solid;margin-left:8px;padding-top:2px;font-family:Fira Code,monospace;display:inline-block;position:relative}.root:before{content:"√";font-size:1.1em;font-weight:700;position:absolute;top:-2px;left:-8px}.topic-check-icon{background:var(--color-primary-100);color:var(--color-primary-700);border-radius:9999px;justify-content:center;align-items:center;width:1.5rem;height:1.5rem;font-size:.75rem;display:flex}.topic-solution-label{color:var(--color-primary-700);margin-left:.5rem;font-weight:600}.topic-solution-text{color:var(--text-secondary);line-height:1.625}