:root{--primary-color:#165DFF;--secondary-color:#4080FF;--success-color:#00B42A;--warning-color:#FF7D00;--danger-color:#F53F3F;--info-color:#86909C;--light-bg:#F2F3F5;--border-color:#E5E6EB;--text-primary:#1D2129;--text-secondary:#4E5969;--text-light:#86909C;--shadow-sm:0 2px 4px rgba(0,0,0,0.05);--shadow-md:0 4px 12px rgba(0,0,0,0.08);--shadow-lg:0 8px 24px rgba(0,0,0,0.12);--border-radius:8px;--transition:all 0.3s ease}*{margin:0;padding:0;box-sizing:border-box}body{min-height:100vh;font-family:-apple-system,BlinkMacSystemFont,'Segoe UI','PingFang SC','Hiragino Sans GB','Microsoft YaHei','Helvetica Neue',Helvetica,Arial,sans-serif;background-color:var(--light-bg);color:var(--text-primary);line-height:1.6}.navbar{background-color:#fff;box-shadow:var(--shadow-sm);z-index:1000}.navbar-brand{font-size:1.25rem;font-weight:600;color:var(--primary-color)!important}.navbar-nav .nav-link{color:var(--text-secondary);font-weight:500;transition:var(--transition);padding:.75rem 1rem}.navbar-nav .nav-link.active,.navbar-nav .nav-link:hover{color:var(--primary-color)}.dropdown-menu{border:1px solid var(--border-color);border-radius:var(--border-radius);box-shadow:var(--shadow-md);padding:.5rem 0}.dropdown-item{padding:.5rem 1.5rem;transition:var(--transition)}.dropdown-item:hover{background-color:var(--light-bg);color:var(--primary-color)}.card{border:none;border-radius:var(--border-radius);box-shadow:var(--shadow-md);transition:var(--transition);overflow:hidden}.card:hover{box-shadow:var(--shadow-lg);transform:translateY(-2px)}.card-header{background-color:#fff;border-bottom:1px solid var(--border-color);font-weight:600;color:var(--text-primary)}.card-body{background-color:#fff}.btn{border-radius:6px;font-weight:500;padding:.5rem 1.25rem;transition:var(--transition);border:none}.btn-primary{background-color:var(--primary-color);color:#fff}.btn-primary:hover{background-color:var(--secondary-color);transform:translateY(-1px)}.btn-success{background-color:var(--success-color);color:#fff}.btn-success:hover{background-color:#00a028}.btn-warning{background-color:var(--warning-color);color:#fff}.btn-warning:hover{background-color:#e67300}.btn-danger{background-color:var(--danger-color);color:#fff}.btn-danger:hover{background-color:#e53838}.btn-outline-primary{border:1px solid var(--primary-color);color:var(--primary-color)}.btn-outline-primary:hover{background-color:var(--primary-color);color:#fff}.form-control{border:1px solid var(--border-color);border-radius:6px;padding:.5rem .75rem;transition:var(--transition)}.form-control:focus{border-color:var(--primary-color);box-shadow:0 0 0 2px rgba(22,93,255,.1);outline:0}.form-label{font-weight:500;color:var(--text-secondary);margin-bottom:.25rem}.badge{border-radius:4px;font-weight:500;padding:.35em .65em}.difficulty-badge{font-size:.85rem;padding:.25em .5em}.table{border-collapse:separate;border-spacing:0}.table thead th{background-color:var(--light-bg);font-weight:600;color:var(--text-primary);border-bottom:2px solid var(--border-color)}.table tbody tr{transition:var(--transition);border-bottom:1px solid var(--border-color)}.table tbody tr:hover{background-color:var(--light-bg)}.status-badge{font-size:.9rem}.status-pending{color:var(--info-color)}.status-judging{color:var(--info-color)}.status-accepted{color:var(--success-color)}.status-wrong_answer{color:var(--danger-color)}.status-time_limit_exceeded{color:var(--danger-color)}.status-memory_limit_exceeded{color:var(--warning-color)}.status-runtime_error{color:var(--danger-color)}.status-compile_error{color:var(--warning-color)}.status-system_error{color:var(--danger-color)}::-webkit-scrollbar{width:6px;height:6px}::-webkit-scrollbar-track{background:var(--light-bg)}::-webkit-scrollbar-thumb{background:#c9cdd4;border-radius:3px}::-webkit-scrollbar-thumb:hover{background:var(--text-light)}pre{font-family:Consolas,Monaco,'Courier New',monospace;font-size:.95rem;line-height:1.5;margin:1rem 0;padding:1.5rem;background-color:#1e1e1e;color:#d4d4d4;border-radius:var(--border-radius);overflow-x:auto;white-space:pre;word-wrap:normal}code{font-family:Consolas,Monaco,'Courier New',monospace;font-size:.9em;background-color:var(--light-bg);color:var(--text-primary);padding:.15em .3em;border-radius:3px}pre code{background-color:transparent;color:inherit;padding:0;border-radius:0}.problem-content{text-align:left;line-height:1.8}.problem-content pre{margin:.5rem 0 1rem 0}.text-primary{color:var(--primary-color)!important}.text-secondary{color:var(--text-secondary)!important}.text-light{color:var(--text-light)!important}.bg-light{background-color:var(--light-bg)!important}.border-radius{border-radius:var(--border-radius)}.shadow-sm{box-shadow:var(--shadow-sm)}.shadow-md{box-shadow:var(--shadow-md)}.shadow-lg{box-shadow:var(--shadow-lg)}.mb-1{margin-bottom:.25rem}.mb-2{margin-bottom:.5rem}.mb-3{margin-bottom:1rem}.mb-4{margin-bottom:1.5rem}.mb-5{margin-bottom:2rem}.mt-1{margin-top:.25rem}.mt-2{margin-top:.5rem}.mt-3{margin-top:1rem}.mt-4{margin-top:1.5rem}.mt-5{margin-top:2rem}.loading-spinner{display:inline-block;width:20px;height:20px;border:2px solid var(--border-color);border-radius:50%;border-top-color:var(--primary-color);animation:spin .8s linear infinite}@keyframes spin{to{transform:rotate(360deg)}}@media (max-width:768px){.navbar-collapse{background-color:#fff;padding:1rem;box-shadow:0 4px 6px rgba(0,0,0,.05)}.card{box-shadow:var(--shadow-sm)}}