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::-webkit-scrollbar-thumb{background:#475569;border-radius:4px}body.dark-mode ::-webkit-scrollbar-thumb:hover{background:#64748b}.highlighted-word{font-weight:700;background:linear-gradient(120deg,#2563eb,#1d4ed8);color:#fff;padding:2px 6px;border-radius:6px;margin:0 1px;display:inline-block;position:relative;cursor:help;transition:all .2s ease;border:1px solid rgba(37,99,235,.3)}.word-tooltip{position:absolute;bottom:100%;left:50%;transform:translate(-50%);background:#000000e6;color:#fff;padding:8px 12px;border-radius:8px;font-size:12px;font-weight:400;white-space:nowrap;opacity:0;visibility:hidden;transition:all .2s ease;z-index:1000;margin-bottom:5px;box-shadow:0 4px 12px #0000004d}.word-tooltip:after{content:"";position:absolute;top:100%;left:50%;transform:translate(-50%);border:5px solid transparent;border-top-color:#000000e6}.tooltip-translation{font-size:13px;margin-bottom:4px;color:#fbbf24;font-weight:500}.tooltip-status{font-size:11px;color:#94a3b8;opacity:.8}.highlighted-word:hover{background:linear-gradient(120deg,#1d4ed8,#1e40af);transform:translateY(-1px);box-shadow:0 3px 8px #2563eb66;border-color:#2563eb99}.highlighted-word:hover .word-tooltip{opacity:1;visibility:visible}.highlighted-word:before{content:"✓";position:absolute;top:-8px;right:-6px;background:#2563eb;color:#fff;font-size:10px;width:14px;height:14px;border-radius:50%;display:flex;align-items:center;justify-content:center;opacity:0;transition:opacity .2s ease;font-weight:700}.highlighted-word:hover:before{opacity:1}.highlighted-word:after{content:"";position:absolute;bottom:-2px;left:50%;transform:translate(-50%);width:0;height:2px;background:#2563eb;transition:width .2s 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.chat-input{color:#e2e8f0;background:transparent}body.dark-mode .chat-input::placeholder{color:#94a3b8}body.dark-mode .send-button{background:#3b82f6}body.dark-mode .send-button:hover:not(:disabled){background:#2563eb}body.dark-mode .send-button:disabled{background:#475569}.welcome-screen{display:flex;flex-direction:column;height:100%;justify-content:center;align-items:center;padding:2rem;max-width:768px;margin:0 auto}.welcome-content{flex:1;display:flex;flex-direction:column;justify-content:center;align-items:center;text-align:center;margin-bottom:2rem}.welcome-header{margin-bottom:3rem}.subject-logo{width:80px;height:80px;background:linear-gradient(135deg,#2563eb,#1d4ed8);border-radius:50%;display:flex;align-items:center;justify-content:center;margin:0 auto 1.5rem;box-shadow:0 8px 24px #2563eb4d}.subject-icon{font-size:32px;color:#fff}.welcome-header h1{font-size:2rem;font-weight:700;color:#1e40af;margin:0 0 1rem}.welcome-header p{font-size:1rem;color:#64748b;line-height:1.5;max-width:500px;margin:0}.suggestions-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:1rem;width:100%;max-width:600px}.suggestion-card{background:#fff;border:2px solid #e2e8f0;border-radius:12px;padding:1rem;cursor:pointer;transition:all .2s ease;text-align:left;display:flex;align-items:flex-start;gap:.75rem;color:#1e293b;font-size:.9rem;line-height:1.4;box-shadow:0 2px 4px #0000000d}.suggestion-card:hover:not(:disabled){background:#f8fafc;border-color:#2563eb;transform:translateY(-2px);box-shadow:0 4px 12px #2563eb26}.suggestion-card:disabled{opacity:.5;cursor:not-allowed}.suggestion-icon{color:#2563eb;flex-shrink:0;margin-top:2px}.welcome-input{width:100%;max-width:768px}.learning-tips{margin-top:2rem;background:#fff;border-radius:12px;padding:1.5rem;max-width:500px;border:2px solid #e2e8f0;box-shadow:0 4px 12px #0000000d}.tip-title{font-size:1rem;font-weight:600;color:#1e40af;margin-bottom:1rem}.tips-list{display:flex;flex-direction:column;gap:.5rem}.tip-item{font-size:.9rem;color:#64748b;line-height:1.4}.loading-dots{display:flex;justify-content:center;gap:4px;margin-top:1rem}.loading-dots .dot{width:8px;height:8px;border-radius:50%;background-color:#2563eb;animation:loading 1.4s infinite ease-in-out both}.loading-dots .dot:nth-child(1){animation-delay:-.32s}.loading-dots .dot:nth-child(2){animation-delay:-.16s}@keyframes loading{0%,80%,to{transform:scale(0);opacity:.5}40%{transform:scale(1);opacity:1}}body.dark-mode .welcome-screen{background:#0f172a;color:#e2e8f0}body.dark-mode .welcome-header h1{color:#3b82f6}body.dark-mode .welcome-header p{color:#94a3b8}body.dark-mode .suggestion-card{background:#1e293b;border-color:#334155;color:#e2e8f0}body.dark-mode .suggestion-card:hover:not(:disabled){background:#334155;border-color:#3b82f6}body.dark-mode 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pre{background:#0f172a;color:#e2e8f0;border-color:#334155}body.dark-mode .close-button{color:#94a3b8}body.dark-mode .close-button:hover{background:#334155;color:#e2e8f0}body.dark-mode .node-summary h3{color:#3b82f6}body.dark-mode .node-summary p,body.dark-mode .node-summary ul{color:#cbd5e1}body.dark-mode .node-summary li:before{color:#3b82f6}