:root{--primary-color:#000000;--primary-hover:#1a1a1a;--secondary-color:#666666;--accent-color:#f5f5f5;--success-color:#22c55e;--danger-color:#ef4444;--warning-color:#f59e0b;--info-color:#3b82f6;--bg-white:#ffffff;--bg-light:#fafafa;--bg-card:#ffffff;--bg-dark:#000000;--text-primary:#000000;--text-secondary:#666666;--text-light:#999999;--text-muted:#cccccc;--text-white:#ffffff;--border-color:#e5e5e5;--border-light:#f0f0f0;--shadow-light:0 2px 10px rgba(0,0,0,0.08);--shadow-medium:0 4px 20px rgba(0,0,0,0.12);--shadow-heavy:0 8px 30px rgba(0,0,0,0.16);--border-radius:8px;--border-radius-lg:12px;--transition:all 0.2s ease;}[data-theme="dark"]{--primary-color:#ffffff;--primary-hover:#e5e5e5;--secondary-color:#999999;--accent-color:#1a1a1a;--success-color:#4ade80;--danger-color:#f87171;--warning-color:#fbbf24;--info-color:#60a5fa;--bg-white:#1a1a1a;--bg-light:#0f0f0f;--bg-card:#1a1a1a;--bg-dark:#000000;--text-primary:#ffffff;--text-secondary:#cccccc;--text-light:#999999;--text-muted:#666666;--text-white:#000000;--border-color:#333333;--border-light:#2a2a2a;--shadow-light:0 2px 10px rgba(0,0,0,0.3);--shadow-medium:0 4px 20px rgba(0,0,0,0.4);--shadow-heavy:0 8px 30px rgba(0,0,0,0.5);}*{margin:0;padding:0;box-sizing:border-box;}*,*::before,*::after{transition:background-color 0.3s ease,border-color 0.3s ease,color 0.3s ease,box-shadow 0.3s ease;}.theme-switching *{transition:none !important;}body{font-family:-apple-system,BlinkMacSystemFont,'Segoe UI','Roboto','Helvetica Neue',Arial,sans-serif;font-size:14px;line-height:1.6;color:var(--text-primary);background-color:var(--bg-light);-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;}.container{max-width:1200px;margin:0 auto;padding:0 1rem;}.app-layout{display:flex;min-height:100vh;background-color:var(--bg-light);}.sidebar{width:280px;background-color:var(--bg-white);border-right:1px solid var(--border-color);padding:2rem 1.5rem;overflow-y:auto;position:fixed;height:100vh;left:0;top:0;box-shadow:var(--shadow-light);}.sidebar::-webkit-scrollbar{width:4px;}.sidebar::-webkit-scrollbar-track{background:transparent;}.sidebar::-webkit-scrollbar-thumb{background:var(--border-color);border-radius:2px;}.main-content{flex:1;margin-left:280px;padding:2rem;background-color:var(--bg-light);min-height:100vh;}h1{font-size:2rem;font-weight:600;margin-bottom:1.5rem;color:var(--text-primary);letter-spacing:-0.02em;}h2{font-size:1.5rem;font-weight:600;margin-bottom:1rem;color:var(--text-primary);letter-spacing:-0.01em;}h3{font-size:1.25rem;font-weight:600;margin-bottom:0.75rem;color:var(--text-primary);}h4{font-size:1.1rem;font-weight:600;margin-bottom:0.5rem;color:var(--text-primary);}p{margin-bottom:1rem;line-height:1.6;color:var(--text-secondary);}small{color:var(--text-light);}.text-muted{color:var(--text-muted);}hr{border:none;height:1px;background-color:var(--border-light);margin:1.5rem 0;}.btn{display:inline-flex;align-items:center;justify-content:center;gap:0.5rem;padding:0.75rem 1.5rem;margin-bottom:0.5rem;font-size:0.875rem;font-weight:500;line-height:1;text-align:center;text-decoration:none;vertical-align:middle;cursor:pointer;border:1px solid transparent;border-radius:var(--border-radius);transition:var(--transition);background:none;outline:none;}.btn:hover{transform:translateY(-1px);box-shadow:var(--shadow-medium);}.btn:active{transform:translateY(0);}.btn-primary{color:var(--text-white);background-color:var(--primary-color);border-color:var(--primary-color);}.btn-primary:hover{background-color:var(--primary-hover);border-color:var(--primary-hover);color:var(--text-white);}.btn-secondary{color:var(--text-primary);background-color:var(--bg-white);border-color:var(--border-color);}.btn-secondary:hover{background-color:var(--accent-color);border-color:var(--border-color);color:var(--text-primary);}.btn-outline-primary{color:var(--primary-color);border-color:var(--primary-color);background-color:transparent;}.btn-outline-primary:hover{color:var(--text-white);background-color:var(--primary-color);border-color:var(--primary-color);}.btn-outline-secondary{color:var(--text-secondary);border-color:var(--border-color);background-color:transparent;}.btn-outline-secondary:hover{color:var(--text-primary);background-color:var(--accent-color);border-color:var(--border-color);}.btn-danger{color:var(--text-white);background-color:var(--danger-color);border-color:var(--danger-color);}.btn-danger:hover{background-color:var(--danger-color);border-color:var(--danger-color);color:var(--text-white);opacity:0.9;}.btn-outline-danger{color:var(--danger-color);border-color:var(--danger-color);background-color:transparent;}.btn-outline-danger:hover{color:var(--text-white);background-color:var(--danger-color);border-color:var(--danger-color);}.btn-block{display:flex;width:100%;margin-bottom:0.75rem;}.btn-lg{padding:1rem 2rem;font-size:1rem;}.btn-sm{padding:0.5rem 1rem;font-size:0.75rem;font-weight:500;}.btn:disabled{opacity:0.5;cursor:not-allowed;transform:none !important;box-shadow:none !important;}.btn-success:disabled{background-color:#22c55e;border-color:#22c55e;color:var(--text-white);opacity:0.8;cursor:not-allowed;}.btn-success:disabled::before{content:'✓ ';font-weight:bold;}.btn-secondary:not(:disabled):hover{background-color:#22c55e;border-color:#22c55e;color:var(--text-white);transform:translateY(-1px);box-shadow:0 4px 12px rgba(34,197,94,0.3);}.btn-success{transition:all 0.3s ease;}.theme-toggle{display:flex;align-items:center;justify-content:space-between;background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--border-radius);padding:0.75rem;margin-bottom:1rem;transition:var(--transition);}.theme-toggle:hover{box-shadow:var(--shadow-light);}.theme-toggle-label{font-size:0.875rem;font-weight:500;color:var(--text-primary);display:flex;align-items:center;gap:0.5rem;}.theme-toggle-switch{position:relative;display:inline-block;width:44px;height:24px;background:var(--border-color);border-radius:12px;transition:var(--transition);cursor:pointer;outline:none;}.theme-toggle-switch:hover{transform:scale(1.05);}.theme-toggle-switch:focus{box-shadow:0 0 0 3px rgba(0,0,0,0.1);}.theme-toggle-switch::before{content:'';position:absolute;top:2px;left:2px;width:20px;height:20px;background:var(--text-primary);border-radius:50%;transition:var(--transition);}.theme-toggle-switch.active{background:var(--primary-color);}.theme-toggle-switch.active::before{transform:translateX(20px);background:var(--text-white);}.theme-icon{font-size:1rem;opacity:0.7;transition:var(--transition);}[data-theme="dark"] .theme-icon.sun{opacity:0.5;}[data-theme="dark"] .theme-icon.moon{opacity:1;}[data-theme="dark"] .form-control::placeholder,[data-theme="dark"] .form-select::placeholder{color:var(--text-light);}[data-theme="dark"] .btn-primary{background-color:var(--primary-color);border-color:var(--primary-color);color:var(--text-white);}[data-theme="dark"] .btn-primary:hover{background-color:var(--primary-hover);border-color:var(--primary-hover);}[data-theme="dark"] .btn-secondary{background-color:var(--bg-card);border-color:var(--border-color);color:var(--text-primary);}[data-theme="dark"] .btn-secondary:hover{background-color:var(--accent-color);border-color:var(--border-color);color:var(--text-primary);}[data-theme="dark"] .btn-outline-primary{border-color:var(--primary-color);color:var(--primary-color);}[data-theme="dark"] .btn-outline-primary:hover{background-color:var(--primary-color);color:var(--text-white);}[data-theme="dark"] .btn-outline-secondary{border-color:var(--secondary-color);color:var(--secondary-color);}[data-theme="dark"] .btn-outline-secondary:hover{background-color:var(--secondary-color);color:var(--text-white);}[data-theme="dark"] .btn-danger{background-color:var(--danger-color);border-color:var(--danger-color);color:var(--text-white);}[data-theme="dark"] .btn-danger:hover{background-color:var(--danger-color);border-color:var(--danger-color);color:var(--text-white);opacity:0.8;}[data-theme="dark"] .btn-outline-danger{border-color:var(--danger-color);color:var(--danger-color);}[data-theme="dark"] .btn-outline-danger:hover{background-color:var(--danger-color);color:var(--text-white);}[data-theme="dark"] .nav-tab.active{background-color:var(--primary-color);color:var(--bg-dark);}[data-theme="dark"] .btn.loading .loading-text{color:var(--bg-dark);}[data-theme="dark"] .btn.loading .loading-text:before{border-top-color:var(--bg-dark);}[data-theme="dark"] .btn.loading.btn-outline-primary .loading-text,[data-theme="dark"] .btn.loading.btn-outline-secondary .loading-text{color:var(--primary-color);}[data-theme="dark"] .btn.loading.btn-outline-primary .loading-text:before,[data-theme="dark"] .btn.loading.btn-outline-secondary .loading-text:before{border-top-color:var(--primary-color);}.form-group{margin-bottom:1.5rem;position:relative;}.form-label{display:block;margin-bottom:0.5rem;font-weight:500;color:var(--text-primary);font-size:0.875rem;transition:color 0.2s ease;position:relative;}.form-label::after{content:' *';color:#e74c3c;font-weight:bold;opacity:0;transition:opacity 0.2s ease;}.form-group:has(.form-control[required]) .form-label::after,.form-group:has(.form-select[required]) .form-label::after{opacity:1;}.form-label:contains("Optional"){color:var(--text-secondary);}.form-control,.form-select{display:block;width:100%;padding:0.75rem 1rem;font-size:0.875rem;font-weight:400;line-height:1.5;color:var(--text-primary);background-color:var(--bg-white);background-image:none;border:1px solid var(--border-color);border-radius:var(--border-radius);transition:all 0.3s cubic-bezier(0.4,0,0.2,1);position:relative;}.form-control:hover,.form-select:hover{border-color:var(--primary-color);box-shadow:0 2px 8px rgba(0,0,0,0.05);transform:translateY(-1px);}.form-control:focus,.form-select:focus{border-color:var(--primary-color);box-shadow:0 0 0 3px rgba(0,0,0,0.1),0 4px 12px rgba(0,0,0,0.05);transform:translateY(-1px);}.form-control::placeholder{color:var(--text-muted);}.form-select{background-image:url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3e%3cpath fill='%23666666' d='M7.247 11.14 2.451 5.658C1.885 5.013 2.345 4 3.204 4h9.592a1 1 0 0 1 .753 1.659l-4.796 5.48a1 1 0 0 1-1.506 0z'/%3e%3c/svg%3e");background-repeat:no-repeat;background-position:right 1rem center;background-size:14px 14px;cursor:pointer;padding-right:3rem;appearance:none;-webkit-appearance:none;-moz-appearance:none;}.form-select:hover{border-color:var(--primary-color);background-image:url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3e%3cpath fill='%23000000' d='M7.247 11.14 2.451 5.658C1.885 5.013 2.345 4 3.204 4h9.592a1 1 0 0 1 .753 1.659l-4.796 5.48a1 1 0 0 1-1.506 0z'/%3e%3c/svg%3e");}.form-select:focus{background-image:url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3e%3cpath fill='%23000000' d='M8.75 4.86 13.546 10.342c.566.645.106 1.658-.753 1.658H3.204a1 1 0 0 1-.753-1.659L7.247 4.861a1 1 0 0 1 1.506 0z'/%3e%3c/svg%3e");}.form-select-wrapper{position:relative;display:block;}.form-select-wrapper::after{content:'';position:absolute;top:50%;right:1rem;transform:translateY(-50%);width:0;height:0;border-left:5px solid transparent;border-right:5px solid transparent;border-top:6px solid var(--text-secondary);pointer-events:none;transition:var(--transition);}.form-select-wrapper:hover::after{border-top-color:var(--primary-color);}.form-select option{padding:0.75rem 1rem;background-color:var(--bg-white);color:var(--text-primary);border:none;line-height:1.4;}.form-select option:checked{background-color:var(--primary-color);color:white;font-weight:500;}.form-select option[value=""]{color:var(--text-muted);font-style:italic;}.form-select option:hover,.form-select option:focus{background-color:var(--bg-light);color:var(--primary-color);}.form-select option:disabled{color:var(--text-muted);font-style:italic;}.form-select.loading{background-image:url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none'%3e%3cpath fill='%23999999' d='M12 2C6.48 2 2 6.48 2 12s4.48 10 10 10 10-4.48 10-10S17.52 2 12 2zm0 16c-3.31 0-6-2.69-6-6s2.69-6 6-6 6 2.69 6 6-2.69 6-6 6z'/%3e%3cpath fill='%23999999' d='M12 6c-3.31 0-6 2.69-6 6h2c0-2.21 1.79-4 4-4V6z'%3e%3canimateTransform attributeName='transform' attributeType='XML' type='rotate' from='0 12 12' to='360 12 12' dur='1s' repeatCount='indefinite'/%3e%3c/path%3e%3c/svg%3e");background-size:16px 16px;background-position:right 1rem center;background-repeat:no-repeat;}.form-select.loading{background-image:url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none'%3e%3cpath fill='%23999999' d='M12 2C6.48 2 2 6.48 2 12s4.48 10 10 10 10-4.48 10-10S17.52 2 12 2zm0 16c-3.31 0-6-2.69-6-6s2.69-6 6-6 6 2.69 6 6-2.69 6-6 6z'/%3e%3cpath fill='%23999999' d='M12 6c-3.31 0-6 2.69-6 6h2c0-2.21 1.79-4 4-4V6z'%3e%3canimateTransform attributeName='transform' attributeType='XML' type='rotate' from='0 12 12' to='360 12 12' dur='1s' repeatCount='indefinite'/%3e%3c/path%3e%3c/svg%3e");}.loading-indicator{display:none;align-items:center;gap:0.5rem;margin-top:0.5rem;padding:0.5rem;background:var(--bg-light);border:1px solid var(--border-color);border-radius:var(--border-radius);font-size:0.875rem;color:var(--text-secondary);}.loading-indicator .spinner{width:16px;height:16px;border:2px solid var(--border-color);border-top:2px solid var(--primary-color);border-radius:50%;animation:spin 1s linear infinite;flex-shrink:0;}@keyframes spin{0%{transform:rotate(0deg);}100%{transform:rotate(360deg);}}.card{background-color:var(--bg-white);border:1px solid var(--border-color);border-radius:var(--border-radius-lg);padding:1.5rem;margin-bottom:1.5rem;box-shadow:var(--shadow-light);transition:var(--transition);}.card:hover{box-shadow:var(--shadow-medium);}.stats-card{background-color:var(--bg-white);border:1px solid var(--border-color);border-radius:var(--border-radius);padding:1.25rem;margin-bottom:1rem;text-align:center;transition:var(--transition);}.stats-card:hover{box-shadow:var(--shadow-light);transform:translateY(-2px);}.stats-number{font-size:2rem;font-weight:700;color:var(--text-primary);margin-bottom:0.25rem;line-height:1;}.stats-label{color:var(--text-secondary);font-size:0.75rem;font-weight:500;text-transform:uppercase;letter-spacing:0.5px;}.nav-tabs{display:flex;background-color:var(--bg-white);border-radius:var(--border-radius-lg);padding:0.25rem;margin-bottom:2rem;border:1px solid var(--border-color);gap:0.25rem;}.nav-tab{flex:1;padding:0.75rem 1rem;background:transparent;border:none;border-radius:var(--border-radius);font-weight:500;color:var(--text-secondary);cursor:pointer;transition:var(--transition);text-align:center;}.nav-tab.active{background-color:var(--primary-color);color:var(--text-white);box-shadow:var(--shadow-light);}.nav-tab:not(.active):hover{background-color:var(--accent-color);color:var(--text-primary);}.tab-content{animation:fadeIn 0.3s ease;}@keyframes fadeIn{from{opacity:0;transform:translateY(10px);}to{opacity:1;transform:translateY(0);}}.alert{padding:1rem 1.5rem;border-radius:var(--border-radius);margin-bottom:1.5rem;border:1px solid var(--border-color);background-color:var(--bg-white);color:var(--text-primary);}.alert-info{background-color:var(--bg-white);border-color:var(--border-color);color:var(--text-primary);}.alert-success{background-color:var(--bg-white);border-color:var(--primary-color);color:var(--text-primary);}.alert-warning{background-color:var(--bg-white);border-color:var(--border-color);color:var(--text-primary);}.alert-danger{background-color:var(--bg-white);border-color:var(--primary-color);color:var(--text-primary);}.row{display:flex;flex-wrap:wrap;margin:0 -0.75rem;}.col-3{flex:0 0 25%;max-width:25%;padding:0 0.75rem;}.col-6{flex:0 0 50%;max-width:50%;padding:0 0.75rem;}.col-8{flex:0 0 66.666667%;max-width:66.666667%;padding:0 0.75rem;}.col-4{flex:0 0 33.333333%;max-width:33.333333%;padding:0 0.75rem;}.col-12{flex:0 0 100%;max-width:100%;padding:0 0.75rem;}.mb-2{margin-bottom:0.5rem;}.mb-3{margin-bottom:1rem;}.mb-4{margin-bottom:1.5rem;}.mb-5{margin-bottom:2rem;}.mt-2{margin-top:0.5rem;}.mt-3{margin-top:1rem;}.mt-4{margin-top:1.5rem;}.text-center{text-align:center;}.text-left{text-align:left;}.text-right{text-align:right;}.d-flex{display:flex;}.justify-content-between{justify-content:space-between;}.align-items-center{align-items:center;}.problem-container{background-color:var(--bg-white);border:1px solid var(--border-color);border-radius:var(--border-radius-lg);padding:2rem;margin-bottom:1.5rem;box-shadow:var(--shadow-light);}.problem-meta{display:flex;gap:0.75rem;margin-bottom:1.5rem;flex-wrap:wrap;}.problem-badge{padding:0.5rem 1rem;border-radius:var(--border-radius);font-size:0.75rem;font-weight:600;text-transform:uppercase;letter-spacing:0.5px;background-color:var(--primary-color);color:var(--text-white);}.problem-content{font-size:1rem;line-height:1.7;margin-bottom:2rem;color:var(--text-primary);}.problem-actions{display:flex;gap:1rem;flex-wrap:wrap;margin-top:2rem;}.options-container{display:grid;gap:0.75rem;margin-bottom:2rem;}.option-box{background-color:var(--bg-white);border:2px solid var(--border-color);border-radius:var(--border-radius);padding:1rem 1.5rem;cursor:pointer;transition:var(--transition);display:flex;align-items:center;gap:1rem;position:relative;}.option-box:hover{border-color:var(--primary-color);box-shadow:var(--shadow-light);}.option-box.selected{border-color:var(--primary-color);background-color:var(--accent-color);}.option-box.correct{border-color:#22c55e;background-color:rgba(34,197,94,0.1);animation:correctAnswer 0.5s ease-out;}.option-box.correct .option-letter{background-color:#22c55e;color:white;}.option-box.incorrect{border-color:#ef4444;background-color:rgba(239,68,68,0.1);animation:incorrectAnswer 0.5s ease-out;}.option-box.incorrect .option-letter{background-color:#ef4444;color:white;}.option-box.correct::before{content:'✓';position:absolute;top:0.5rem;right:0.5rem;width:24px;height:24px;background-color:#22c55e;color:white;border-radius:50%;display:flex;align-items:center;justify-content:center;font-size:14px;font-weight:bold;animation:fadeInCheck 0.3s ease-out 0.2s both;}.option-box.incorrect::before{content:'✗';position:absolute;top:0.5rem;right:0.5rem;width:24px;height:24px;background-color:#ef4444;color:white;border-radius:50%;display:flex;align-items:center;justify-content:center;font-size:14px;font-weight:bold;animation:fadeInCheck 0.3s ease-out 0.2s both;}@keyframes fadeInCheck{0%{opacity:0;transform:scale(0);}100%{opacity:1;transform:scale(1);}}.option-box.selected.incorrect{border-color:#ef4444;background-color:rgba(239,68,68,0.15);box-shadow:0 0 0 3px rgba(239,68,68,0.2);}.option-box.selected.correct{border-color:#22c55e;background-color:rgba(34,197,94,0.15);box-shadow:0 0 0 3px rgba(34,197,94,0.2);}@keyframes correctAnswer{0%{transform:scale(1);box-shadow:0 0 0 0 rgba(34,197,94,0.7);}50%{transform:scale(1.02);box-shadow:0 0 0 10px rgba(34,197,94,0);}100%{transform:scale(1);box-shadow:0 0 0 0 rgba(34,197,94,0);}}@keyframes incorrectAnswer{0%{transform:translateX(0);}25%{transform:translateX(-5px);}75%{transform:translateX(5px);}100%{transform:translateX(0);}}.option-letter{width:32px;height:32px;border-radius:50%;background-color:var(--primary-color);color:var(--text-white);display:flex;align-items:center;justify-content:center;font-weight:600;font-size:0.875rem;flex-shrink:0;}.option-text{flex:1;font-size:0.875rem;line-height:1.5;}.saved-problem-item{background-color:var(--bg-white);border:1px solid var(--border-color);border-radius:var(--border-radius);padding:1.5rem;margin-bottom:1rem;transition:var(--transition);}.saved-problem-item:hover{box-shadow:var(--shadow-light);transform:translateY(-2px);}.problem-title{font-weight:600;margin-bottom:0.5rem;color:var(--text-primary);}.problem-metadata{display:flex;gap:0.75rem;margin-bottom:1rem;flex-wrap:wrap;}.metadata-item{background-color:var(--accent-color);color:var(--text-secondary);padding:0.25rem 0.75rem;border-radius:var(--border-radius);font-size:0.75rem;font-weight:500;}.loading{display:flex;align-items:center;justify-content:center;padding:2rem;color:var(--text-secondary);}.spinner{width:20px;height:20px;border:2px solid var(--border-color);border-top:2px solid var(--primary-color);border-radius:50%;animation:spin 1s linear infinite;margin-right:0.5rem;}@keyframes spin{0%{transform:rotate(0deg);}100%{transform:rotate(360deg);}}@media (max-width:1024px){.sidebar{width:260px;}.main-content{margin-left:260px;padding:1.5rem;}}@media (max-width:768px){.sidebar{width:100%;position:relative;height:auto;box-shadow:none;border-right:none;border-bottom:1px solid var(--border-color);}.main-content{margin-left:0;padding:1rem;}.row{margin:0;}.col-3,.col-4,.col-6,.col-8{flex:0 0 100%;max-width:100%;padding:0;margin-bottom:1rem;}.problem-meta{flex-direction:column;gap:0.5rem;}.problem-actions{flex-direction:column;}.nav-tabs{flex-direction:column;gap:0.5rem;}.nav-tab{text-align:center;}.form-select{font-size:16px;padding:1rem;background-size:16px 16px;background-position:right 1rem center;}.form-select option{padding:1rem 0.75rem;font-size:16px;}}.btn:focus,.form-control:focus,.form-select:focus,.nav-tab:focus{outline:2px solid var(--primary-color);outline-offset:2px;}html{scroll-behavior:smooth;}.alert-info{color:#0c5460;background-color:#d1ecf1;border-color:#bee5eb;}.nav-tabs{display:flex;border-bottom:1px solid var(--border-color);margin-bottom:1rem;}.nav-tab{padding:0.5rem 1rem;margin-right:0.25rem;background-color:transparent;border:1px solid transparent;border-bottom:none;border-top-left-radius:0.375rem;border-top-right-radius:0.375rem;color:var(--secondary-color);text-decoration:none;cursor:pointer;}.nav-tab.active{background-color:#fff;border-color:var(--border-color);border-bottom-color:#fff;color:var(--dark-color);}.nav-tab:hover:not(.active){border-color:var(--hover-color);}.row{display:flex;flex-wrap:wrap;margin-right:-0.75rem;margin-left:-0.75rem;}.col{flex:1;padding-right:0.75rem;padding-left:0.75rem;}.col-2{flex:0 0 16.666667%;max-width:16.666667%;}.col-3{flex:0 0 25%;max-width:25%;}.col-4{flex:0 0 33.333333%;max-width:33.333333%;}.col-6{flex:0 0 50%;max-width:50%;}.col-8{flex:0 0 66.666667%;max-width:66.666667%;}.col-12{flex:0 0 100%;max-width:100%;}.text-center{text-align:center;}.text-left{text-align:left;}.text-right{text-align:right;}.mb-1{margin-bottom:0.25rem;}.mb-2{margin-bottom:0.5rem;}.mb-3{margin-bottom:1rem;}.mb-4{margin-bottom:1.5rem;}.mb-5{margin-bottom:3rem;}.mt-1{margin-top:0.25rem;}.mt-2{margin-top:0.5rem;}.mt-3{margin-top:1rem;}.mt-4{margin-top:1.5rem;}.mt-5{margin-top:3rem;}.d-none{display:none;}.d-block{display:block;}.d-flex{display:flex;}.loading{opacity:0.6;pointer-events:none;}.spinner{display:inline-block;width:1rem;height:1rem;border:2px solid #f3f3f3;border-top:2px solid var(--primary-color);border-radius:50%;animation:spin 1s linear infinite;}.btn.loading{position:relative;cursor:not-allowed;opacity:0.8;}.btn.loading .loading-text{display:flex;align-items:center;justify-content:center;gap:0.5rem;color:var(--text-white);font-size:0.875rem;white-space:nowrap;}.btn.loading.btn-outline-primary .loading-text,.btn.loading.btn-outline-secondary .loading-text{color:var(--primary-color);}.btn.loading .loading-text:before{content:'';width:1rem;height:1rem;border:2px solid transparent;border-top:2px solid var(--text-white);border-radius:50%;animation:spin 1s linear infinite;flex-shrink:0;}.btn.loading.btn-outline-primary .loading-text:before,.btn.loading.btn-outline-secondary .loading-text:before{border-top-color:var(--primary-color);}@media (max-width:768px){.sidebar{position:static;width:100%;height:auto;}.main-content{margin-left:0;padding:1rem;}.app-layout{flex-direction:column;}.col-3,.col-4,.col-6,.col-8{flex:0 0 100%;max-width:100%;margin-bottom:1rem;}h1{font-size:2rem;}h2{font-size:1.5rem;}}.hero-section{text-align:center;padding:4rem 0;background:linear-gradient(135deg,#667eea 0%,#764ba2 100%);color:white;margin-bottom:3rem;}.hero-title{font-size:3.5rem;font-weight:700;margin-bottom:1rem;}.hero-subtitle{font-size:1.25rem;font-weight:300;margin-bottom:2rem;opacity:0.9;}.feature-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:2rem;margin:3rem 0;}.feature-card{background:white;padding:2rem;border-radius:10px;box-shadow:0 4px 6px rgba(0,0,0,0.1);text-align:center;transition:transform 0.3s ease;}.feature-card:hover{transform:translateY(-5px);}.feature-icon{font-size:3rem;margin-bottom:1rem;}.app-header{background-color:#fff;border-bottom:1px solid var(--border-color);padding:1rem 0;position:sticky;top:0;z-index:100;margin-left:300px;}.header-content{display:flex;justify-content:space-between;align-items:center;padding:0 2rem;}.user-info{display:flex;align-items:center;gap:1rem;}.user-avatar{width:32px;height:32px;border-radius:50%;}@media (max-width:768px){.app-header{margin-left:0;}}.form-section{background:var(--bg-white);border-radius:var(--border-radius-lg);padding:1.5rem;margin-bottom:1.5rem;border:1px solid var(--border-color);box-shadow:var(--shadow-light);}.form-section h3{color:var(--text-primary);font-size:1.125rem;font-weight:600;margin-bottom:1rem;border-bottom:1px solid var(--border-color);padding-bottom:0.5rem;}.form-group{transition:all 0.2s ease;}.form-group:focus-within{transform:translateY(-1px);}.form-group:focus-within .form-label{color:var(--primary-color);font-weight:600;}.math-fallback{font-family:'Courier New',Consolas,'Monaco',monospace !important;background-color:#f8f9fa !important;border:1px solid #dee2e6 !important;border-radius:4px !important;padding:2px 6px !important;margin:0 2px !important;display:inline-block !important;font-size:0.9em !important;color:#495057 !important;position:relative !important;cursor:help !important;}.math-fallback:hover{background-color:#e9ecef !important;border-color:#adb5bd !important;}.math-fallback::before{content:"📝";position:absolute;top:-8px;right:-8px;font-size:12px;background:white;border-radius:50%;width:16px;height:16px;display:flex;align-items:center;justify-content:center;border:1px solid #dee2e6;}@media (max-width:768px){.math-fallback::before{display:none;}}