:root{--primary-color: #007bff;--primary-hover: #0056b3;--secondary-color: #6c757d;--secondary-hover: #5a6268;--danger-color: #dc3545;--danger-hover: #c82333;--success-color: #28a745;--warning-color: #ffc107;--error-color: #dc3545;--correct-bg: #d4edda;--correct-text: #155724;--correct-border: #c3e6cb;--incorrect-bg: #f8d7da;--incorrect-text: #721c24;--incorrect-border: #f5c6cb;--border-radius: 8px;--box-shadow: 0 2px 8px rgba(0, 0, 0, .1);--transition: all .3s ease}*{margin:0;padding:0;box-sizing:border-box}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen,Ubuntu,Cantarell,Fira Sans,Droid Sans,Helvetica Neue,sans-serif;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;background-color:#f5f5f5;color:#333}.loading-screen{display:flex;justify-content:center;align-items:center;min-height:100vh;font-size:24px;color:var(--primary-color)}.loading{text-align:center;padding:40px;color:var(--primary-color);font-size:18px}.error{padding:20px;background-color:var(--incorrect-bg);border:1px solid var(--incorrect-border);border-radius:var(--border-radius);color:var(--incorrect-text);text-align:center}.error-message{background-color:var(--incorrect-bg);border:1px solid var(--incorrect-border);border-radius:var(--border-radius);color:var(--incorrect-text);padding:12px;margin-bottom:16px;font-weight:500}button{cursor:pointer;font-size:16px;border:none;border-radius:var(--border-radius);padding:10px 20px;font-weight:500;transition:var(--transition);font-family:inherit}.btn-primary{background-color:var(--primary-color);color:#fff;padding:12px 24px;font-size:16px}.btn-primary:hover:not(:disabled){background-color:var(--primary-hover);transform:translateY(-2px);box-shadow:0 4px 12px #007bff4d}.btn-primary:disabled{background-color:var(--secondary-color);cursor:not-allowed;opacity:.6}.btn-secondary{background-color:var(--secondary-color);color:#fff;padding:10px 16px}.btn-secondary:hover:not(:disabled){background-color:var(--secondary-hover);transform:translateY(-2px);box-shadow:0 4px 12px #6c757d4d}.btn-secondary:disabled{cursor:not-allowed;opacity:.6}.btn-danger{background-color:var(--danger-color);color:#fff;padding:10px 16px}.btn-danger:hover:not(:disabled){background-color:var(--danger-hover);transform:translateY(-2px);box-shadow:0 4px 12px #dc35454d}button[type=button],button[type=submit]{cursor:pointer}.auth-container{display:flex;justify-content:center;align-items:center;min-height:100vh;background:linear-gradient(135deg,#667eea,#764ba2);padding:20px}.auth-card{background:#fff;border-radius:var(--border-radius);box-shadow:0 10px 30px #0003;padding:40px;width:100%;max-width:400px}.auth-card h1{font-size:28px;margin-bottom:10px;text-align:center;color:#333}.auth-card h2{font-size:20px;margin-bottom:30px;text-align:center;color:var(--primary-color)}.auth-card form{display:flex;flex-direction:column;gap:16px}.auth-card input{padding:12px;border:1px solid #ddd;border-radius:var(--border-radius);font-size:16px;transition:var(--transition)}.auth-card input:focus{outline:none;border-color:var(--primary-color);box-shadow:0 0 0 3px #007bff1a}.auth-card button{padding:12px;font-size:16px;margin-top:8px}.toggle-auth{text-align:center;margin-top:20px;font-size:14px;color:#666}.toggle-auth button{background:none;color:var(--primary-color);text-decoration:underline;padding:0;margin-left:4px;font-size:14px}.toggle-auth button:hover{color:var(--primary-hover)}.page{min-height:100vh;background-color:#f5f5f5}.app-header{background-color:#fff;border-bottom:1px solid #ddd;box-shadow:var(--box-shadow);position:sticky;top:0;z-index:100}.header-content{display:flex;justify-content:space-between;align-items:center;padding:20px;max-width:1200px;margin:0 auto}.app-header h1{font-size:24px;color:#333;margin:0}.user-info{display:flex;align-items:center;gap:20px}.user-info span{font-size:16px;color:#666}.quiz-list-container{max-width:1200px;margin:0 auto;padding:40px 20px}.quiz-list-container h2{font-size:28px;margin-bottom:30px;color:#333}.quiz-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:24px}.quiz-card{background:#fff;border-radius:var(--border-radius);padding:24px;box-shadow:var(--box-shadow);transition:var(--transition);display:flex;flex-direction:column}.quiz-card:hover{transform:translateY(-4px);box-shadow:0 8px 16px #00000026}.quiz-card h3{font-size:20px;margin-bottom:12px;color:#333}.quiz-card .description{color:#666;font-size:14px;margin-bottom:16px;flex-grow:1}.quiz-meta{display:flex;gap:12px;margin-bottom:16px;flex-wrap:wrap}.badge{display:inline-block;padding:6px 12px;border-radius:20px;font-size:12px;font-weight:600}.badge.difficulty{background-color:#fff3cd;color:#856404}.badge.questions{background-color:#d1ecf1;color:#0c5460}.quiz-card a{text-decoration:none;background-color:var(--primary-color);color:#fff;padding:12px;border-radius:var(--border-radius);text-align:center;transition:var(--transition);display:inline-block;width:100%;border:none;cursor:pointer;font-weight:500}.quiz-card a:hover{background-color:var(--primary-hover);transform:translateY(-2px)}.empty-state{text-align:center;padding:60px 20px;color:#999}.empty-state p{font-size:18px}.quiz-header{background-color:#fff;border-bottom:1px solid #ddd;padding:20px;position:sticky;top:0;z-index:50}.header-top{display:flex;align-items:center;gap:20px;max-width:1200px;margin:0 auto}.back-link{color:var(--primary-color);text-decoration:none;font-weight:500;transition:var(--transition)}.back-link:hover{color:var(--primary-hover)}.header-top h1{font-size:24px;margin:0;flex-grow:1}.progress-bar{max-width:1200px;margin:16px auto;height:8px;background-color:#e0e0e0;border-radius:4px;overflow:hidden}.progress-fill{height:100%;background-color:var(--success-color);transition:width .3s ease}.progress-text{max-width:1200px;margin:0 auto;padding:0 20px;font-size:14px;color:#666;text-align:right}.quiz-container{max-width:1000px;margin:0 auto;padding:40px 20px;display:grid;grid-template-columns:1fr 280px;gap:24px}@media (max-width: 768px){.quiz-container{grid-template-columns:1fr}}.question-card{background:#fff;border-radius:var(--border-radius);padding:32px;box-shadow:var(--box-shadow)}.question-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:24px;padding-bottom:16px;border-bottom:2px solid #f0f0f0}.question-number{font-size:14px;color:var(--primary-color);font-weight:600}.question-category{font-size:12px;background-color:#f0f0f0;padding:6px 12px;border-radius:20px;color:#666}.question-text{font-size:18px;font-weight:600;margin-bottom:28px;color:#333;line-height:1.6}.answers-container{display:flex;flex-direction:column;gap:12px;margin-bottom:28px}.answer-option{display:flex;align-items:flex-start;padding:16px;border:2px solid #e0e0e0;border-radius:var(--border-radius);cursor:pointer;transition:var(--transition);background-color:#fff}.answer-option:hover:not([disabled]){border-color:var(--primary-color);background-color:#f9f9f9}.answer-option input[type=checkbox]{margin-right:12px;margin-top:4px;cursor:pointer;width:18px;height:18px;accent-color:var(--primary-color)}.answer-option span{flex-grow:1;line-height:1.5}.answer-option.selected{border-color:var(--primary-color);background-color:#007bff0d}.answer-option.correct-selected{border-color:var(--success-color);background-color:var(--correct-bg)}.answer-option.correct-unselected{border-color:#28a745;background-color:var(--correct-bg);opacity:.7}.answer-option.incorrect-selected{border-color:var(--error-color);background-color:var(--incorrect-bg)}.answer-option input[type=checkbox]:disabled{cursor:not-allowed;opacity:.7}.feedback{padding:16px;border-radius:var(--border-radius);margin-bottom:24px;animation:slideDown .3s ease}@keyframes slideDown{0%{opacity:0;transform:translateY(-10px)}to{opacity:1;transform:translateY(0)}}.feedback.correct{background-color:var(--correct-bg);border:1px solid var(--correct-border);color:var(--correct-text)}.feedback.incorrect{background-color:var(--incorrect-bg);border:1px solid var(--incorrect-border);color:var(--incorrect-text)}.feedback h4{margin:0 0 8px;font-size:16px}.feedback p{margin:0;font-size:14px}.button-group{display:flex;gap:12px}.button-group button{flex:1;padding:14px;font-size:16px}.navigation-buttons{display:flex;gap:12px;justify-content:space-between;align-items:center}.navigation-buttons button{flex:1;padding:14px}.quiz-complete{text-align:center;padding:14px;background-color:var(--success-color);color:#fff;border-radius:var(--border-radius);font-weight:600}.quiz-sidebar{display:flex;flex-direction:column;gap:20px}.stats-card{background:#fff;border-radius:var(--border-radius);padding:20px;box-shadow:var(--box-shadow)}.stats-card h3{font-size:16px;margin-bottom:16px;color:#333}.stat-item{display:flex;justify-content:space-between;align-items:center;padding:12px 0;border-bottom:1px solid #f0f0f0}.stat-item:last-child{border-bottom:none}.stat-item span{color:#666;font-size:14px}.stat-item strong{color:var(--primary-color);font-size:16px;font-weight:600}.stats-card .btn-danger{width:100%;margin-top:8px}@media (max-width: 768px){.auth-card{max-width:90%}.header-content{flex-direction:column;gap:16px;text-align:center}.user-info{justify-content:center}.question-header{flex-direction:column;gap:12px;align-items:flex-start}.navigation-buttons{flex-direction:column}.quiz-grid{grid-template-columns:1fr}}@media (max-width: 480px){.question-card{padding:16px}.question-text{font-size:16px}.button-group{flex-direction:column}}