:root{--primary: #1976d2;--primary-light: #42a5f5;--primary-dark: #1565c0;--secondary: #dc004e;--accent: #ff6f00;--success: #4caf50;--warning: #ff9800;--danger: #f44336;--bg-light: #fafafa;--bg-white: #ffffff;--surface: #ffffff;--text-primary: rgba(0, 0, 0, .87);--text-secondary: rgba(0, 0, 0, .6);--text-disabled: rgba(0, 0, 0, .38);--divider: rgba(0, 0, 0, .12);--elevation-1: 0 2px 4px rgba(0, 0, 0, .1);--elevation-2: 0 4px 8px rgba(0, 0, 0, .12);--elevation-4: 0 8px 16px rgba(0, 0, 0, .14);--elevation-8: 0 16px 24px rgba(0, 0, 0, .16);--transition: all .3s cubic-bezier(.4, 0, .2, 1);--transition-fast: all .15s cubic-bezier(.4, 0, .2, 1)}*{margin:0;padding:0;box-sizing:border-box}body{font-family:Roboto,Segoe UI,Tahoma,Geneva,Verdana,sans-serif;background:linear-gradient(135deg,#e3f2fd,#bbdefb);color:var(--text-primary);min-height:100vh;line-height:1.6;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}.App{min-height:100vh;background:var(--bg-light)}.header{background:var(--primary);color:#fff;padding:16px 32px;display:flex;justify-content:space-between;align-items:center;box-shadow:var(--elevation-4);position:sticky;top:0;z-index:1000;transition:var(--transition)}.app-title{display:flex;align-items:center;gap:12px;font-size:1.5rem;font-weight:500;color:#fff;letter-spacing:.5px}.rocket-icon{font-size:2rem;animation:float 3s ease-in-out infinite}@keyframes float{0%,to{transform:translateY(0)}50%{transform:translateY(-8px)}}.user-profile{display:flex;align-items:center;gap:16px;cursor:pointer;padding:8px 16px;border-radius:24px;transition:var(--transition)}.user-profile:hover{background:#ffffff1a;transform:translateY(-2px)}.user-profile:active{transform:translateY(0)}.avatar{width:48px;height:48px;border-radius:50%;background:linear-gradient(135deg,#ff6b6b,#feca57);display:flex;align-items:center;justify-content:center;font-weight:600;font-size:1.2rem;color:#fff;box-shadow:var(--elevation-2);transition:var(--transition)}.user-profile:hover .avatar{box-shadow:var(--elevation-4);transform:scale(1.05)}.user-info{display:flex;flex-direction:column;gap:6px}.username{font-weight:500;font-size:.95rem;color:#fff}.xp-bar{width:100px;height:4px;background:#ffffff4d;border-radius:4px;overflow:hidden}.xp-fill{height:100%;background:linear-gradient(90deg,#feca57,#ff6b6b);transition:width .5s cubic-bezier(.4,0,.2,1);box-shadow:0 0 8px #feca5799}.level-badge{background:#fff3;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);padding:6px 14px;border-radius:16px;font-weight:600;font-size:.9rem;color:#fff;border:2px solid rgba(255,255,255,.3);transition:var(--transition)}.user-profile:hover .level-badge{background:#ffffff4d;border-color:#ffffff80}.nav-tabs{display:flex;background:var(--surface);padding:8px 24px;gap:8px;overflow-x:auto;box-shadow:var(--elevation-2);border-bottom:1px solid var(--divider)}.nav-tab{padding:12px 24px;border-radius:24px;cursor:pointer;transition:var(--transition);white-space:nowrap;display:flex;align-items:center;gap:10px;color:var(--text-secondary);font-weight:500;position:relative;overflow:hidden}.nav-tab:before{content:"";position:absolute;top:50%;left:50%;width:0;height:0;border-radius:50%;background:#1976d21a;transform:translate(-50%,-50%);transition:width .6s,height .6s}.nav-tab:hover:before{width:300px;height:300px}.nav-tab:hover{background:#1976d214;color:var(--primary);transform:translateY(-2px)}.nav-tab:active{transform:translateY(0)}.nav-tab.active{background:var(--primary);color:#fff;box-shadow:var(--elevation-2)}.nav-tab.active:hover{background:var(--primary-dark)}.tab-icon{font-size:1.3rem;transition:var(--transition)}.nav-tab:hover .tab-icon{transform:scale(1.1)}.container{max-width:1200px;margin:32px auto;padding:0 24px}.card{background:var(--surface);border-radius:16px;padding:32px;box-shadow:var(--elevation-2);margin-bottom:24px;transition:var(--transition);position:relative;overflow:hidden}.card:before{content:"";position:absolute;top:0;left:0;right:0;height:4px;background:linear-gradient(90deg,var(--primary),var(--primary-light));transform:scaleX(0);transform-origin:left;transition:transform .3s ease}.card:hover{box-shadow:var(--elevation-4);transform:translateY(-4px)}.card:hover:before{transform:scaleX(1)}.timer-card{position:relative;text-align:center;background:linear-gradient(135deg,#fff,#f5f5f5)}.motivation-message{margin-bottom:32px;padding:20px;background:linear-gradient(135deg,#1976d21a,#42a5f51a);border-radius:12px;animation:fadeIn .5s ease}@keyframes fadeIn{0%{opacity:0;transform:translateY(-10px)}to{opacity:1;transform:translateY(0)}}.motivation-message h3{color:var(--primary);margin-bottom:12px;font-weight:500;font-size:1.3rem}.timer-settings{display:flex;justify-content:center;gap:20px;margin-bottom:20px;flex-wrap:wrap}.form-group{display:flex;flex-direction:column;gap:8px}.form-group label{font-size:.9rem;font-weight:600}.form-group select,.form-group input,.form-group textarea{padding:14px 16px;border-radius:8px;border:2px solid var(--divider);background:var(--surface);color:var(--text-primary);font-family:inherit;font-size:1rem;transition:var(--transition);box-shadow:inset 0 2px 4px #0000000d}.form-group select:focus,.form-group input:focus,.form-group textarea:focus{outline:none;border-color:var(--primary);box-shadow:0 0 0 3px #1976d21a}.form-group textarea{resize:vertical;min-height:100px;line-height:1.6}.timer-display{font-size:6rem;font-weight:300;margin:32px 0;color:var(--primary);font-family:Roboto Mono,monospace;letter-spacing:8px;text-shadow:0 4px 12px rgba(25,118,210,.2);transition:var(--transition);animation:pulse 2s ease-in-out infinite}@keyframes pulse{0%,to{transform:scale(1)}50%{transform:scale(1.02)}}.study-mode .timer-display{color:var(--primary);text-shadow:0 4px 12px rgba(25,118,210,.3)}.break-mode .timer-display{color:var(--success);text-shadow:0 4px 12px rgba(76,175,80,.3)}.progress-bar{width:100%;height:8px;background:var(--divider);border-radius:8px;overflow:hidden;margin-bottom:32px;box-shadow:inset 0 2px 4px #0000001a}.progress-fill{height:100%;background:linear-gradient(90deg,var(--primary),var(--primary-light));transition:width 1s cubic-bezier(.4,0,.2,1);box-shadow:0 0 12px #1976d280;position:relative}.progress-fill:after{content:"";position:absolute;inset:0;background:linear-gradient(90deg,transparent,rgba(255,255,255,.3),transparent);animation:shimmer 2s infinite}@keyframes shimmer{0%{transform:translate(-100%)}to{transform:translate(100%)}}.timer-mode-switcher{display:flex;justify-content:center;gap:15px;margin-bottom:25px}.btn{padding:12px 32px;border:none;border-radius:24px;cursor:pointer;font-weight:500;transition:var(--transition);font-size:1rem;text-transform:uppercase;letter-spacing:.5px;position:relative;overflow:hidden;box-shadow:var(--elevation-2)}.btn:before{content:"";position:absolute;top:50%;left:50%;width:0;height:0;border-radius:50%;background:#ffffff4d;transform:translate(-50%,-50%);transition:width .6s,height .6s}.btn:active:before{width:300px;height:300px;transition:width 0s,height 0s}.btn:disabled{opacity:.5;cursor:not-allowed;box-shadow:none}.btn-primary{background:var(--primary);color:#fff}.btn-primary:hover:not(:disabled){background:var(--primary-dark);transform:translateY(-2px);box-shadow:var(--elevation-4)}.btn-primary:active:not(:disabled){transform:translateY(0);box-shadow:var(--elevation-2)}.btn-secondary{background:var(--surface);color:var(--text-primary);border:1px solid var(--divider)}.btn-secondary:hover:not(:disabled){background:var(--bg-light);border-color:var(--primary);transform:translateY(-2px);box-shadow:var(--elevation-4)}.btn-tertiary{background:var(--danger);color:#fff}.btn-tertiary:hover:not(:disabled){background:#d32f2f;transform:translateY(-2px);box-shadow:var(--elevation-4)}.btn-mode{background:var(--surface);color:var(--text-secondary);border:2px solid var(--divider);box-shadow:none}.btn-mode:hover:not(:disabled){border-color:var(--primary);color:var(--primary)}.btn-mode.active{background:var(--primary);color:#fff;border-color:var(--primary);box-shadow:var(--elevation-2)}.btn-mode.active:hover{background:var(--primary-dark)}.subject-buttons{display:flex;gap:12px;justify-content:center;flex-wrap:wrap;margin:24px 0 32px}.subject-btn{padding:12px 24px;border:2px solid var(--divider);background:var(--surface);color:var(--text-secondary);border-radius:24px;cursor:pointer;transition:var(--transition);font-weight:500;box-shadow:var(--elevation-1);position:relative;overflow:hidden}.subject-btn:before{content:"";position:absolute;top:0;left:-100%;width:100%;height:100%;background:linear-gradient(90deg,transparent,rgba(25,118,210,.1),transparent);transition:left .5s}.subject-btn:hover:before{left:100%}.subject-btn:hover{border-color:var(--primary);color:var(--primary);transform:translateY(-2px);box-shadow:var(--elevation-2)}.subject-btn.active{background:var(--primary);border-color:var(--primary);color:#fff;box-shadow:var(--elevation-2);transform:scale(1.05)}.subject-btn.active:hover{background:var(--primary-dark)}.timer-controls{display:flex;justify-content:center;gap:15px;flex-wrap:wrap}.stats-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:24px;margin-top:32px}.stat-item{text-align:center;padding:24px;background:linear-gradient(135deg,#fff,#f8f9fa);border-radius:16px;transition:var(--transition);position:relative;overflow:hidden}.stat-item:before{content:"";position:absolute;top:0;left:0;right:0;height:4px;background:linear-gradient(90deg,var(--primary),var(--primary-light))}.stat-item:hover{transform:translateY(-8px) scale(1.02);box-shadow:var(--elevation-8)}.stat-number{font-size:3.5rem;font-weight:300;color:var(--primary);display:block;margin-bottom:8px;animation:countUp .5s ease}@keyframes countUp{0%{opacity:0;transform:translateY(20px)}to{opacity:1;transform:translateY(0)}}.stat-label{font-size:.95rem;color:var(--text-secondary);font-weight:500}.badges-container{display:grid;grid-template-columns:repeat(auto-fill,minmax(140px,1fr));gap:20px;margin-top:24px}.badge{padding:24px;border-radius:16px;text-align:center;transition:var(--transition);cursor:pointer;position:relative;overflow:hidden}.badge:before{content:"";position:absolute;top:-50%;left:-50%;width:200%;height:200%;background:radial-gradient(circle,rgba(255,255,255,.3),transparent);opacity:0;transition:opacity .3s}.badge:hover:before{opacity:1;animation:rotate 3s linear infinite}@keyframes rotate{0%{transform:rotate(0)}to{transform:rotate(360deg)}}.badge.earned{background:linear-gradient(135deg,var(--primary),var(--primary-light));box-shadow:var(--elevation-2);color:#fff}.badge.unearned{background:var(--bg-light);border:2px dashed var(--divider);opacity:.6;color:var(--text-disabled)}.badge:hover{transform:translateY(-8px) scale(1.05);box-shadow:var(--elevation-8)}.badge.earned:hover{box-shadow:0 12px 32px #1976d266}.badge-icon{font-size:2.5rem;display:block;margin-bottom:12px;transition:var(--transition)}.badge:hover .badge-icon{transform:scale(1.2) rotate(10deg)}.badge-name{font-size:.95rem;font-weight:500}.note-form{margin-top:20px}.note-form .form-group{margin-bottom:20px}.note-form .btn{width:100%}.qa-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:20px}.question-list{display:flex;flex-direction:column;gap:15px}.question-item{padding:24px;background:var(--surface);border-radius:12px;cursor:pointer;transition:var(--transition);border-left:4px solid transparent;box-shadow:var(--elevation-1)}.question-item:hover{background:var(--bg-light);transform:translate(8px);border-left-color:var(--primary);box-shadow:var(--elevation-4)}.subject-tag{display:inline-block;padding:6px 16px;background:linear-gradient(135deg,var(--primary),var(--primary-light));color:#fff;border-radius:20px;font-size:.85rem;font-weight:500;margin-bottom:12px;box-shadow:var(--elevation-1)}.question-item h3{margin:12px 0;font-size:1.15rem;font-weight:500;color:var(--text-primary)}.question-meta{display:flex;gap:24px;font-size:.9rem;color:var(--text-secondary);margin-top:12px}@media (max-width: 768px){.header{padding:12px 16px}.app-title{font-size:1.2rem}.user-profile{gap:8px;padding:4px 8px}.avatar{width:40px;height:40px}.nav-tabs{padding:8px 12px;gap:6px}.nav-tab{padding:10px 16px;font-size:.9rem}.container{padding:0 16px;margin:16px auto}.card{padding:20px}.timer-display{font-size:4rem;letter-spacing:4px}.stats-grid{grid-template-columns:repeat(2,1fr);gap:16px}.stat-number{font-size:2.5rem}.badges-container{grid-template-columns:repeat(auto-fill,minmax(100px,1fr));gap:12px}.btn{padding:10px 20px;font-size:.9rem}}@media (max-width: 480px){.timer-display{font-size:3rem}.stats-grid{grid-template-columns:1fr}.subject-buttons{gap:8px}.subject-btn{padding:8px 16px;font-size:.9rem}}::-webkit-scrollbar{width:10px;height:10px}::-webkit-scrollbar-track{background:var(--bg-light)}::-webkit-scrollbar-thumb{background:var(--primary);border-radius:5px}::-webkit-scrollbar-thumb:hover{background:var(--primary-dark)}::selection{background:var(--primary);color:#fff}@keyframes spin{0%{transform:rotate(0)}to{transform:rotate(360deg)}}.ripple{position:relative;overflow:hidden}.ripple:after{content:"";position:absolute;top:50%;left:50%;width:0;height:0;border-radius:50%;background:#ffffff80;transform:translate(-50%,-50%);transition:width .6s,height .6s}.ripple:active:after{width:300px;height:300px;transition:width 0s,height 0s}h2{color:var(--text-primary);font-weight:500;font-size:1.75rem;margin-bottom:16px}h3{color:var(--text-primary);font-weight:500;font-size:1.25rem;margin-bottom:12px}a{color:var(--primary);text-decoration:none;transition:var(--transition)}a:hover{color:var(--primary-dark);text-decoration:underline}*:focus-visible{outline:2px solid var(--primary);outline-offset:2px}.subject-stats{display:flex;flex-direction:column;gap:20px;margin-top:20px}.subject-stat-item{padding:16px;background:var(--bg-light);border-radius:12px;transition:var(--transition)}.subject-stat-item:hover{transform:translate(4px);box-shadow:var(--elevation-2)}.subject-stat-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}.subject-stat-name{font-weight:500;color:var(--text-primary)}.subject-stat-time{font-weight:600;color:var(--primary);font-size:1.1rem}.subject-stat-bar{width:100%;height:8px;background:var(--divider);border-radius:8px;overflow:hidden}.subject-stat-fill{height:100%;background:linear-gradient(90deg,var(--primary),var(--primary-light));transition:width .5s cubic-bezier(.4,0,.2,1);box-shadow:0 0 8px #1976d266}.modal{display:none;position:fixed;inset:0;background:#00000080;z-index:2000;align-items:center;justify-content:center;-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px)}.modal.active{display:flex}.modal-content{background:var(--surface);border-radius:16px;max-width:500px;width:90%;max-height:90vh;overflow-y:auto;box-shadow:var(--elevation-8);animation:modalSlideIn .3s ease}@keyframes modalSlideIn{0%{opacity:0;transform:translateY(-50px)}to{opacity:1;transform:translateY(0)}}.modal-header{display:flex;justify-content:space-between;align-items:center;padding:20px 24px;border-bottom:1px solid var(--divider)}.modal-header h3{margin:0;font-size:1.25rem;font-weight:500}.close-modal{background:none;border:none;font-size:2rem;cursor:pointer;color:var(--text-secondary);transition:var(--transition);width:40px;height:40px;display:flex;align-items:center;justify-content:center;border-radius:50%}.close-modal:hover{background:var(--bg-light);color:var(--text-primary)}.university-list{margin-top:24px}.university-buttons{display:grid;grid-template-columns:repeat(auto-fill,minmax(200px,1fr));gap:12px;margin-top:16px}.university-btn{padding:16px;border:2px solid var(--divider);background:var(--surface);color:var(--text-primary);border-radius:12px;cursor:pointer;transition:var(--transition);font-weight:500;text-align:left}.university-btn:hover{border-color:var(--primary);background:var(--bg-light);transform:translateY(-2px);box-shadow:var(--elevation-2)}.university-btn.active{background:var(--primary);border-color:var(--primary);color:#fff;box-shadow:var(--elevation-2)}.user-rank-card{display:flex;align-items:center;gap:20px;padding:20px;background:linear-gradient(135deg,#1976d21a,#42a5f51a);border-radius:12px;margin-bottom:24px;border:2px solid var(--primary)}.rank-badge{font-size:2rem;font-weight:700;color:var(--primary);min-width:60px;text-align:center}.ranking-list{display:flex;flex-direction:column;gap:12px}.ranking-item{display:flex;align-items:center;gap:16px;padding:16px;background:var(--bg-light);border-radius:12px;transition:var(--transition)}.ranking-item:hover{background:var(--surface);transform:translate(4px);box-shadow:var(--elevation-2)}.ranking-item.user-ranking{background:linear-gradient(135deg,#1976d226,#42a5f526);border:2px solid var(--primary)}.rank-number{font-size:1.5rem;font-weight:700;min-width:50px;text-align:center}.ranking-user-info{display:flex;align-items:center;gap:12px;flex:1}.ranking-avatar{width:40px;height:40px;border-radius:50%;background:linear-gradient(135deg,var(--primary),var(--primary-light));display:flex;align-items:center;justify-content:center;color:#fff;font-weight:600}.ranking-name{font-weight:500;display:flex;align-items:center;gap:8px}.ranking-level{font-size:.85rem;color:var(--text-secondary)}.ranking-time{font-size:1.2rem;font-weight:600;color:var(--primary);min-width:80px;text-align:right}.online-badge{font-size:.7rem;animation:blink 2s infinite}@keyframes blink{0%,to{opacity:1}50%{opacity:.5}}.add-friend-form{padding:20px;background:var(--bg-light);border-radius:12px}.btn-remove-friend{background:none;border:none;color:var(--text-secondary);font-size:1.5rem;cursor:pointer;width:32px;height:32px;border-radius:50%;transition:var(--transition);display:flex;align-items:center;justify-content:center}.btn-remove-friend:hover{background:var(--danger);color:#fff}.recommended-users{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:16px}.recommended-user-card{display:flex;align-items:center;gap:16px;padding:16px;background:var(--bg-light);border-radius:12px;transition:var(--transition)}.recommended-user-card:hover{background:var(--surface);box-shadow:var(--elevation-2);transform:translateY(-2px)}.notes-feed{display:flex;flex-direction:column;gap:20px;margin-top:20px}.note-card{background:var(--bg-light);border-radius:12px;padding:20px;transition:var(--transition)}.note-card:hover{box-shadow:var(--elevation-2);transform:translateY(-2px)}.note-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:16px}.note-user{display:flex;align-items:center;gap:12px}.note-username{font-weight:500;color:var(--text-primary)}.note-time{font-size:.85rem;color:var(--text-secondary)}.note-content{display:flex;flex-direction:column;gap:16px}.note-section{padding:12px;background:var(--surface);border-radius:8px}.note-section strong{display:block;margin-bottom:8px;color:var(--primary)}.note-section p{color:var(--text-primary);line-height:1.6}.note-footer{margin-top:16px;padding-top:16px;border-top:1px solid var(--divider)}.btn-like{background:none;border:2px solid var(--divider);padding:8px 16px;border-radius:20px;cursor:pointer;transition:var(--transition);font-size:.95rem;color:var(--text-secondary)}.btn-like:hover{border-color:var(--primary);color:var(--primary);background:#1976d20d}.qa-filters{display:flex;gap:8px;margin:20px 0;flex-wrap:wrap}.filter-btn{padding:8px 16px;border:2px solid var(--divider);background:var(--surface);color:var(--text-secondary);border-radius:20px;cursor:pointer;transition:var(--transition);font-size:.9rem}.filter-btn:hover{border-color:var(--primary);color:var(--primary)}.filter-btn.active{background:var(--primary);border-color:var(--primary);color:#fff}.answer-card{padding:16px;background:var(--bg-light);border-radius:12px;margin-bottom:16px}.answer-form{margin-top:32px;padding-top:24px;border-top:2px solid var(--divider)}.answer-form h4{margin-bottom:16px;color:var(--text-primary)}