:root{--color-primary:#5b6ee8;--color-primary-dark:#6b5bb5;--color-primary-light:#eef0ff;--color-bg:#f4f6f9;--color-surface:#fff;--color-text:#1f2937;--color-text-secondary:#6b7280;--color-text-muted:#9ca3af;--color-border:#e5e7eb;--color-border-hover:#c7d2fe;--color-easy:#2e7d32;--color-easy-bg:#e8f5e9;--color-medium:#e65100;--color-medium-bg:#fff3e0;--color-hard:#c62828;--color-hard-bg:#ffebee;--color-danger:#dc3545;--color-warning:#b8860b;--color-warning-bg:#fffbe6;--gradient-primary:linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));--radius-sm:6px;--radius-md:10px;--radius-lg:12px;--radius-full:999px;--shadow-sm:0 1px 3px #0000000a;--shadow-md:0 4px 16px #0000000f;--shadow-lg:0 8px 24px #00000014;--font-family:-apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;--font-mono:"Menlo", "Consolas", monospace;--max-width:1000px;--navbar-height:56px;--spacing-page:24px}*,:before,:after{box-sizing:border-box;margin:0;padding:0}html{scrollbar-gutter:stable;overflow-y:scroll}body{font-family:var(--font-family);background:var(--color-bg);color:var(--color-text);-webkit-font-smoothing:antialiased;min-height:100vh;line-height:1.6}a{color:var(--color-primary)}img{max-width:100%}.btn{border-radius:var(--radius-md);cursor:pointer;white-space:nowrap;border:none;justify-content:center;align-items:center;gap:6px;padding:10px 20px;font-family:inherit;font-size:14px;font-weight:600;text-decoration:none;transition:opacity .2s,transform .15s,background .15s,border-color .15s;display:inline-flex}.btn:disabled{opacity:.5;cursor:not-allowed;transform:none}.btn-primary{background:var(--gradient-primary);color:#fff}.btn-primary:hover:not(:disabled){opacity:.92}.btn-outline{background:var(--color-surface);color:var(--color-primary);border:1px solid var(--color-primary)}.btn-outline:hover:not(:disabled){background:var(--color-primary-light)}.btn-ghost{background:var(--color-surface);color:var(--color-text-secondary);border:1px solid var(--color-border)}.btn-ghost:hover:not(:disabled){border-color:var(--color-primary);color:var(--color-primary)}.btn-danger{background:var(--color-surface);color:var(--color-danger);border:1px solid var(--color-border)}.btn-danger:hover:not(:disabled){border-color:var(--color-danger);background:#fff0f0}.btn-sm{padding:6px 14px;font-size:13px}.btn-action{border:1px solid var(--color-border);border-radius:var(--radius-sm);background:var(--color-surface);cursor:pointer;color:var(--color-text-secondary);padding:7px 16px;font-family:inherit;font-size:13px;text-decoration:none;transition:all .15s;display:inline-block}.btn-action:hover{border-color:var(--color-primary);color:var(--color-primary)}.btn-action--primary{background:var(--color-primary);color:#fff;border-color:var(--color-primary)}.btn-action--primary:hover{opacity:.88;color:#fff}.btn-action--danger:hover{border-color:var(--color-danger);color:var(--color-danger)}.btn-action--active{background:var(--color-warning-bg);color:var(--color-warning);border-color:#f0d060}.badge{border-radius:var(--radius-full);white-space:nowrap;padding:3px 10px;font-size:12px;font-weight:500}.badge--easy{background:var(--color-easy-bg);color:var(--color-easy)}.badge--medium{background:var(--color-medium-bg);color:var(--color-medium)}.badge--hard{background:var(--color-hard-bg);color:var(--color-hard)}.badge--mistake{background:var(--color-warning-bg);color:var(--color-warning);border:1px solid #f0d060}.tag{background:var(--color-primary-light);color:var(--color-primary);border-radius:var(--radius-full);padding:4px 12px;font-size:12px;display:inline-block}.tag--clickable{cursor:pointer;text-decoration:none;transition:background .15s}.tag--clickable:hover{background:#dde2ff}.mini-tag{background:var(--color-primary-light);color:var(--color-primary);border-radius:var(--radius-full);padding:2px 8px;font-size:11px}.page-header{flex-wrap:wrap;justify-content:space-between;align-items:center;gap:12px;margin-bottom:20px;display:flex}.page-header h2{color:var(--color-text);font-size:22px;font-weight:600}.page-header__meta{color:var(--color-text-muted);font-size:14px}.state{text-align:center;background:var(--color-surface);border-radius:var(--radius-lg);color:var(--color-text-muted);border:1px solid var(--color-border);padding:56px 20px}.state__icon{opacity:.6;margin-bottom:12px;font-size:40px}.state--error{color:var(--color-danger)}.state__actions{flex-wrap:wrap;justify-content:center;gap:10px;margin-top:16px;display:flex}.loading-dots:after{content:"";animation:1.2s steps(4,end) infinite dots}@keyframes dots{0%{content:""}25%{content:"."}50%{content:".."}75%{content:"..."}}.spinner{border:3px solid var(--color-border);border-top-color:var(--color-primary);border-radius:50%;width:32px;height:32px;margin:0 auto 12px;animation:.7s linear infinite spin}@keyframes spin{to{transform:rotate(360deg)}}.back-link{color:var(--color-primary);margin-bottom:16px;font-size:14px;font-weight:500;text-decoration:none;display:inline-block}.back-link:hover{text-decoration:underline}.surface-card{background:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-lg);padding:20px;transition:box-shadow .2s,border-color .2s}.surface-card--hover:hover{box-shadow:var(--shadow-md);border-color:var(--color-border-hover)}.list-item{background:var(--color-surface);border-radius:var(--radius-md);border:1px solid var(--color-border);color:inherit;align-items:center;gap:12px;padding:14px 18px;text-decoration:none;transition:box-shadow .15s,border-color .15s;display:flex}.list-item:hover{box-shadow:var(--shadow-sm);border-color:var(--color-border-hover)}.list-item__title{color:var(--color-text);text-overflow:ellipsis;white-space:nowrap;flex:1;min-width:0;font-size:15px;font-weight:500;overflow:hidden}.list-item:hover .list-item__title{color:var(--color-primary)}.list-item__meta{color:var(--color-text-muted);flex-shrink:0;font-size:12px}.list-item__tags{flex-shrink:0;gap:4px;display:flex}.auth-page{max-width:400px;margin:48px auto;padding:0 20px}.auth-card{background:var(--color-surface);border-radius:var(--radius-lg);box-shadow:var(--shadow-md);border:1px solid var(--color-border);padding:36px}.auth-card h2{text-align:center;color:var(--color-text);margin-bottom:24px;font-size:22px}.auth-link{text-align:center;color:var(--color-text-muted);margin-top:16px;font-size:14px}.auth-link a{font-weight:500;text-decoration:none}.auth-link a:hover{text-decoration:underline}.error-msg{color:var(--color-danger);border-radius:var(--radius-sm);background:#fff0f0;margin-bottom:16px;padding:10px 14px;font-size:14px}.form-group{margin-bottom:16px}.form-group label{color:var(--color-text-secondary);margin-bottom:6px;font-size:14px;font-weight:500;display:block}.form-group input,.form-group select,.form-group textarea{border:1px solid var(--color-border);border-radius:var(--radius-md);background:var(--color-surface);outline:none;width:100%;padding:10px 14px;font-family:inherit;font-size:15px;transition:border-color .2s,box-shadow .2s}.form-group input:focus,.form-group select:focus,.form-group textarea:focus{border-color:var(--color-primary);box-shadow:0 0 0 3px #5b6ee81f}.filter-bar{flex-wrap:wrap;align-items:center;gap:12px;margin-bottom:20px;display:flex}.search-box{flex:1;min-width:200px;position:relative}.search-box input{border:1px solid var(--color-border);border-radius:var(--radius-md);background:var(--color-surface);outline:none;width:100%;padding:10px 36px;font-size:14px;transition:border-color .2s,box-shadow .2s}.search-box input:focus{border-color:var(--color-primary);box-shadow:0 0 0 3px #5b6ee81f}.search-box__icon{color:var(--color-text-muted);pointer-events:none;font-size:14px;position:absolute;top:50%;left:12px;transform:translateY(-50%)}.search-box__clear{color:var(--color-text-muted);cursor:pointer;background:0 0;border:none;padding:4px;font-size:14px;position:absolute;top:50%;right:10px;transform:translateY(-50%)}.search-box__clear:hover{color:var(--color-text)}.filter-bar__group{flex-wrap:wrap;align-items:center;gap:8px;display:flex}.filter-bar select{border:1px solid var(--color-border);border-radius:var(--radius-md);background:var(--color-surface);cursor:pointer;outline:none;min-width:120px;padding:10px 14px;font-family:inherit;font-size:14px}.filter-bar select:focus{border-color:var(--color-primary)}.toggle-btn{border:1px solid var(--color-border);border-radius:var(--radius-md);background:var(--color-surface);cursor:pointer;white-space:nowrap;color:var(--color-text-secondary);padding:10px 16px;font-family:inherit;font-size:13px;transition:all .2s}.toggle-btn.active{border-color:var(--color-danger);color:var(--color-danger);background:#fff0f0}.pagination{flex-wrap:wrap;justify-content:center;align-items:center;gap:4px;margin-top:28px;display:flex}.pagination button{border:1px solid var(--color-border);border-radius:var(--radius-sm);background:var(--color-surface);cursor:pointer;color:var(--color-text-secondary);padding:8px 14px;font-family:inherit;font-size:14px;transition:all .15s}.pagination button:hover:not(:disabled):not(.active){border-color:var(--color-primary);color:var(--color-primary)}.pagination button.active{background:var(--color-primary);color:#fff;border-color:var(--color-primary)}.pagination button:disabled{opacity:.35;cursor:not-allowed}.pagination__ellipsis{color:var(--color-text-muted);padding:0 6px}.pagination__total{color:var(--color-text-muted);margin-left:12px;font-size:13px}.markdown-body{color:var(--color-text);font-size:15px;line-height:1.75}.markdown-body code{background:#f3f4f6;border-radius:4px;padding:2px 6px;font-size:13px}.markdown-body pre{color:#f8f8f2;border-radius:var(--radius-md);background:#2d2d2d;margin:12px 0;padding:16px;font-size:13px;line-height:1.6;overflow-x:auto}.markdown-body pre code{background:0 0;padding:0}.markdown-body h2,.markdown-body h3,.markdown-body h4{color:var(--color-text);margin:16px 0 8px}.markdown-body p{margin-bottom:10px}.markdown-body ul,.markdown-body ol{margin:8px 0;padding-left:22px}.markdown-body blockquote{border-left:3px solid var(--color-primary);color:var(--color-text-secondary);margin:12px 0;padding-left:14px}