.theme-btn{background:transparent;border:1px solid var(--border-light);color:var(--text-main);width:38px;height:38px;border-radius:50%;display:flex;align-items:center;justify-content:center;cursor:pointer;transition:all .3s ease;font-size:1.2rem}.theme-btn:hover{background:var(--bg-button);transform:rotate(20deg)}.mode-container{max-width:var(--container-width);margin:0 auto;padding:0 1.5rem;display:flex;justify-content:flex-end}.revision-mode-btn{background:var(--bg-card);border:2px solid var(--warning);color:var(--warning);padding:6px 16px;border-radius:30px;font-weight:700;cursor:pointer;transition:all .3s ease;font-size:.85rem;display:flex;align-items:center;gap:6px}.revision-mode-btn.active{background:var(--warning);color:#121212;transform:scale(1.05)}main{max-width:var(--container-width);margin:0 auto;padding:0 1.5rem;min-height:60vh}.question-card{background:var(--bg-card);border-radius:var(--radius);padding:1rem;margin-bottom:1rem;box-shadow:var(--shadow-card);border:1px solid var(--border-light);transition:all .3s ease}.question-card:hover{transform:translateY(-2px);border-color:var(--primary-accent)}.question-card.is-mastered{border-color:var(--success)}.question-card.is-important{border-left:5px solid var(--warning)}.q-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:1.2rem;flex-wrap:wrap;gap:10px;border-bottom:1px dashed var(--border-light);padding-bottom:1rem}.q-badge{background:var(--primary-surface);color:var(--primary-accent);padding:5px 12px;border-radius:8px;font-size:.8rem;font-weight:700}.q-controls{display:flex;gap:10px;align-items:center}.q-timer{background:var(--bg-secondary);color:var(--success);padding:5px 12px;border-radius:20px;font-size:.8rem;font-weight:700;font-family:monospace;border:1px solid var(--border-light)}.toggle-btn{display:inline-flex;align-items:center;gap:6px;padding:6px 14px;border-radius:20px;font-size:.85rem;font-weight:600;background:var(--bg-button);color:var(--text-main);border:1px solid var(--border-light);cursor:pointer;white-space:nowrap}.toggle-btn::before{font-size:1rem;line-height:1}.imp-btn::before{content:"★";color:var(--warning)}.mast-btn::before{content:"✔";color:var(--success)}.imp-btn.active{background:var(--warning);color:#121212;border-color:var(--warning)}.imp-btn.active::before{color:#121212}.mast-btn.active{background:var(--success);color:#fff;border-color:var(--success)}.mast-btn.active::before{color:#fff}.question-text{font-weight:600;font-size:1.1rem;margin:1.5rem 0;color:var(--text-main);line-height:1.7}.solution-btn{background:var(--bg-card);border:2px solid var(--primary);color:var(--primary);padding:12px;border-radius:12px;font-weight:700;cursor:pointer;width:100%;transition:all .3s;margin-top:1rem}.solution-btn:hover{background:var(--primary-surface)}.solution-btn.active{background:var(--primary);color:white}.solution-content{display:none;margin-top:1.5rem;padding:1.5rem;background:var(--bg-secondary);border-radius:12px;border-left:4px solid var(--success);animation:slideDown .3s ease-out;color:var(--text-main)}@keyframes slideDown{from{opacity:0;transform:translateY(-10px)}to{opacity:1;transform:translateY(0)}}.step{margin-bottom:1rem;position:relative;padding-left:15px}.step::before{content:'';position:absolute;left:0;top:9px;width:6px;height:6px;background:var(--success);border-radius:50%}.step strong{color:var(--success);font-size:.9rem;text-transform:uppercase;margin-right:5px}.final-ans{font-weight:700;color:var(--primary-accent);border-top:1px dashed var(--border-light);margin-top:15px;padding-top:10px}@media (max-width:768px){.header-content{padding:0 1rem}nav{display:none}.nav-container{flex-direction:row;gap:10px;margin:1.5rem auto}.footer-grid{grid-template-columns:1fr;text-align:center;gap:2.5rem}.footer-col{align-items:center}.footer-col h3::after{left:50%;transform:translateX(-50%)}.footer-brand p{margin:1rem auto}.q-header{justify-content:center;text-align:center}.q-controls{justify-content:center;width:100%;margin-top:10px}}.solution-content.open{display:block}.nav-buttons,.nav-container{max-width:var(--container-width);margin:1.5rem auto;padding:0 1rem;display:flex;gap:1rem}.nav-btn{flex:1;text-align:center;padding:14px 16px;border-radius:14px;font-weight:600;font-size:.9rem;text-decoration:none;transition:all .25s ease;border:1.5px solid var(--border-light);background:var(--bg-card);color:var(--text-main);box-shadow:var(--shadow-card);animation:fadeInUpBtn .6s ease-out}.nav-btn.btn-prev{background:var(--bg-secondary)}.nav-btn.btn-next{background:var(--primary);color:#fff;border-color:var(--primary)}.nav-btn:hover{transform:translateY(-2px)}@keyframes fadeInUpBtn{from{opacity:0;transform:translateY(15px)}to{opacity:1;transform:translateY(0)}}.nav-btn.disabled{pointer-events:none;opacity:.4;border-style:dashed}.sj-footer{background:#0e0e0f;color:#cfcfd4;border-top:2px solid var(--primary);padding:3rem 1.5rem 1.5rem}.sj-footer-container{max-width:var(--container-width);margin:0 auto;display:flex;justify-content:space-between;align-items:center;gap:2rem;flex-wrap:wrap}.sj-footer-brand{max-width:420px}.sj-footer-brand .logo{font-size:1.5rem;font-weight:800;color:white;text-decoration:none}.sj-footer-brand p{margin-top:.6rem;font-size:.9rem;color:#b6b6bb;line-height:1.6}.sj-footer-links{display:flex;gap:1.5rem}.sj-footer-links a{color:#cfcfd4;font-weight:600;text-decoration:none;transition:color .2s ease}.sj-footer-links a:hover{color:var(--primary)}.sj-footer-bottom{margin-top:2.5rem;padding-top:1rem;border-top:1px solid #1e1e22;text-align:center;font-size:.85rem;color:#9a9aa0}@media (max-width:768px){.sj-footer-container{flex-direction:column;text-align:center}.sj-footer-links{justify-content:center}}.question{margin-bottom:24px}.q-text{font-size:1.05rem;font-weight:500}.exam-instruction{font-size:.8rem;color:#555;margin-top:4px;font-style:italic}.sample-paper-nav{background:var(--bg-card);border-bottom:1px solid var(--border-light);padding:1rem 0;margin-bottom:2rem;overflow-x:auto}.sp-nav-inner{max-width:var(--container-width);margin:0 auto;padding:0 1.5rem;display:flex;align-items:center;gap:1rem}.sp-nav-label{font-weight:600;color:var(--text-muted);white-space:nowrap}.sp-nav-list{display:flex;gap:.5rem}.sp-nav-link{padding:.5rem 1.2rem;border-radius:50px;background:var(--bg-secondary);color:var(--text-main);font-size:.9rem;font-weight:600;text-decoration:none;transition:all .2s;white-space:nowrap;border:1px solid transparent}.sp-nav-link:hover{background:var(--primary-surface);color:var(--primary);border-color:var(--primary)}.sp-nav-link.active{background:var(--primary);color:white;border-color:var(--primary)}mjx-container{overflow-x:auto;overflow-y:hidden;max-width:100%}mjx-container[jax=CHTML]{max-width:100%!important;overflow-x:auto;white-space:normal!important}mjx-container[jax=CHTML] mjx-math{max-width:100%}.question-card mjx-container{display:block;overflow-x:auto}@media (max-width:768px){.nav-buttons,.nav-container{flex-direction:row;gap:.75rem}.nav-btn{padding:12px;font-size:.85rem;border-radius:12px}.sj-footer-brand{margin:0 auto;text-align:center}.sj-footer-brand .logo{justify-content:center;display:flex}.nav-buttons{position:fixed;bottom:0;left:0;width:100%;max-width:100%;background:var(--bg-card);padding:12px 1rem;margin:0;border-top:1px solid var(--border-light);z-index:1000;box-shadow:0 -4px 20px rgba(0,0,0,.08)}body{padding-bottom:90px}}@media (max-width:600px){mjx-container{font-size:.95em}}.question-text mjx-container{display:inline-block!important;max-width:100%;vertical-align:middle}.question-text{line-height:1.6;white-space:normal}.table-wrapper{overflow-x:auto;margin:1.5rem 0;border-radius:12px;border:1px solid var(--border-light);box-shadow:0 2px 8px rgba(0,0,0,.02)}.data-table{width:100%;border-collapse:collapse;font-size:.9rem}.data-table th,.data-table td{padding:12px 16px;border:1px solid var(--border-light);text-align:center;white-space:nowrap}.data-table th{background:var(--bg-secondary);color:var(--text-main);font-weight:700;text-align:left;min-width:80px}