:root{--bg: #faf8f5;--bg-card: #ffffff;--text: #2c3e50;--text-secondary: #6b7d8e;--accent: #0ea5a0;--accent-hover: #0d8c88;--border: #e8e3dc;--success: #27ae60;--error: #e74c3c;--warning: #f39c12;--sidebar-width: 200px;--font-serif: "Noto Serif SC", "Source Han Serif SC", "SimSun", serif;--font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;--radius: 8px}*{margin:0;padding:0;box-sizing:border-box}html,body,#root{height:100%;font-family:var(--font-sans);color:var(--text);background:var(--bg);writing-mode:horizontal-tb!important;direction:ltr}body{-webkit-font-smoothing:antialiased}button{cursor:pointer;font-family:inherit;font-size:14px;border:none;border-radius:var(--radius);padding:8px 20px;transition:all .15s ease}button.primary{background:var(--accent);color:#fff}button.primary:hover{background:var(--accent-hover)}button.primary:disabled{opacity:.5;cursor:not-allowed}button.secondary{background:transparent;color:var(--text);border:1px solid var(--border)}button.secondary:hover{background:var(--border)}button.secondary:disabled{opacity:.4;cursor:not-allowed}input,select,textarea{font-family:inherit;font-size:14px;padding:8px 12px;border:1px solid var(--border);border-radius:var(--radius);background:var(--bg-card);color:var(--text);outline:none}input:focus,select:focus,textarea:focus{border-color:var(--accent)}::-webkit-scrollbar{width:6px}::-webkit-scrollbar-track{background:transparent}::-webkit-scrollbar-thumb{background:var(--border);border-radius:3px}.flip-card{perspective:1000px;cursor:pointer;min-height:420px;touch-action:manipulation;-webkit-tap-highlight-color:transparent;user-select:none;-webkit-user-select:none}@media(min-height:700px){.flip-card{min-height:60vh}}@media(min-height:900px){.flip-card{min-height:65vh}}.flip-card-inner{position:relative;width:100%;transition:transform .5s ease;transform-style:preserve-3d}.flip-card-inner.flipped{transform:rotateY(180deg)}.flip-card-front,.flip-card-back{backface-visibility:hidden;-webkit-backface-visibility:hidden;border-radius:12px;padding:32px 40px;background:var(--bg-card, #fff);border:1px solid var(--border);box-shadow:0 2px 12px #0000000f}@media(max-width:768px){.flip-card-front,.flip-card-back{padding:16px}}.flip-card-back{position:absolute;top:0;left:0;right:0;bottom:0;transform:rotateY(180deg);overflow-y:auto}.flashcard-answer{font-size:24px;font-weight:700;color:var(--accent, #0ea5a0);background:#0ea5a014;border-radius:8px;padding:16px;margin:12px 0;text-align:center}.flashcard-answer.answer-correct{color:#27ae60;background:#27ae6014}.flashcard-answer.answer-wrong{color:#e74c3c;background:#e74c3c14}.flashcard-analysis{margin-top:16px;padding-top:16px;border-top:1px dashed var(--border);font-size:14px;color:var(--text-secondary);line-height:1.7}.flashcard-actions{display:flex;gap:16px;justify-content:center;margin-top:20px}.flashcard-btn{padding:10px 32px;border-radius:8px;font-size:16px;font-weight:600;border:none;cursor:pointer;transition:all .15s ease}.flashcard-btn.forgot{background:#fdecea;color:#e74c3c}.flashcard-btn.forgot:hover{background:#fce4e4}.flashcard-btn.remembered{background:#e6f9f0;color:#27ae60}.flashcard-btn.remembered:hover{background:#d4f5e3}.flashcard-progress{display:flex;align-items:center;gap:16px;justify-content:center;padding:12px 0;font-size:14px;color:var(--text-secondary)}.flashcard-progress .remaining{font-weight:600;color:var(--accent);font-size:18px}.flashcard-picker-list{max-height:400px;overflow-y:auto;border:1px solid var(--border);border-radius:8px}.flashcard-picker-item{display:flex;align-items:center;gap:10px;padding:10px 14px;border-bottom:1px solid var(--border-light, #f0f0f0);cursor:pointer;transition:background .1s;font-size:14px}.flashcard-picker-item:hover{background:#0ea5a00a}.flashcard-picker-item.done{color:#aaa;font-style:italic}.flashcard-picker-item .done-icon{font-size:12px;margin-left:auto}.flashcard-picker-item .type-tag{font-size:11px;padding:2px 6px;border-radius:4px;background:var(--bg-muted, #f5f5f5);color:var(--text-secondary);flex-shrink:0}.flashcard-picker-item .stem-preview{flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.flashcard-summary-overlay{position:fixed;top:0;right:0;bottom:0;left:0;background:#0006;display:flex;align-items:center;justify-content:center;z-index:100}.flashcard-summary{background:#fff;border-radius:16px;padding:32px;max-width:420px;width:90%;box-shadow:0 8px 32px #00000026}.flashcard-summary h3{text-align:center;margin-bottom:20px;font-size:20px}.flashcard-summary .stat-row{display:flex;justify-content:space-between;padding:8px 0;font-size:15px;border-bottom:1px solid var(--border-light, #f0f0f0)}.flashcard-summary .hard-list{margin-top:16px}.flashcard-summary .hard-list h4{font-size:14px;color:var(--text-secondary);margin-bottom:8px}.flashcard-summary .hard-item{font-size:13px;padding:6px 10px;background:#fef5e7;border-radius:6px;margin-bottom:6px;display:flex;align-items:center;gap:8px}.flashcard-summary .hard-item .count{font-weight:700;color:#e67e22;font-size:16px;min-width:28px}@media(max-width:768px){:root{--sidebar-width: 0px}html,body{font-size:15px;-webkit-tap-highlight-color:transparent}button{min-height:44px;padding:10px 16px}input,select,textarea{font-size:16px;padding:10px 14px}}.mobile-nav-toggle{display:none}@media(max-width:768px){.mobile-nav-toggle{display:flex;position:fixed;top:12px;left:12px;z-index:1000;width:44px;height:44px;align-items:center;justify-content:center;background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius);font-size:20px;cursor:pointer;box-shadow:0 2px 8px #00000014}}.mobile-sidebar-overlay{display:none}@media(max-width:768px){.mobile-sidebar-overlay.open{display:block;position:fixed;top:0;right:0;bottom:0;left:0;z-index:999;background:#0006}}.mobile-bottom-nav{display:none}@media(max-width:768px){.mobile-bottom-nav{display:flex;position:fixed;bottom:0;left:0;right:0;z-index:1000;background:var(--bg-card);border-top:1px solid var(--border);padding:6px 0 env(safe-area-inset-bottom,8px);justify-content:space-around;align-items:flex-start;box-shadow:0 -2px 12px #00000014}.mobile-bottom-nav-link{display:flex;flex-direction:column;align-items:center;gap:2px;padding:6px 2px;min-width:0;flex:1;text-decoration:none;color:var(--text-secondary);font-size:11px;border-radius:8px;transition:color .15s;-webkit-tap-highlight-color:transparent}.mobile-bottom-nav-link.active{color:var(--accent)}.mobile-bottom-nav-icon{font-size:22px;line-height:1}.mobile-bottom-nav-label{white-space:nowrap;font-weight:500}}.mobile-sidebar-panel{display:none}@media(max-width:768px){.mobile-sidebar-panel.open{display:flex;position:fixed;top:0;left:0;bottom:0;width:220px;z-index:1000;flex-direction:column;background:var(--bg-card);border-right:1px solid var(--border);padding:60px 0 24px;box-shadow:2px 0 12px #0000001f}}