:root{--bg:#0d1117;--bg-secondary:#161b22;--text:#c9d1d9;--text-muted:#8b949e;--border:#30363d;--link:#58a6ff;--easy:#3fb950;--medium:#d29922;--hard:#f85149;--tag-bg:#21262d;}*{box-sizing:border-box;margin:0;padding:0;}body{font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,Oxygen,Ubuntu,sans-serif;background:var(--bg);color:var(--text);line-height:1.6;min-height:100vh;display:flex;flex-direction:column;}a{color:var(--link);text-decoration:none;}a:hover{text-decoration:underline;}header{background:var(--bg-secondary);border-bottom:1px solid var(--border);padding:1rem 2rem;}header nav{max-width:1200px;margin:0 auto;display:flex;gap:2rem;align-items:center;}header .logo{font-weight:bold;font-size:1.25rem;color:var(--text);}.nav-search{margin-left:auto;position:relative;}.nav-search input{padding:0.4rem 0.75rem;background:var(--bg);border:1px solid var(--border);border-radius:6px;color:var(--text);font-size:0.875rem;width:250px;}.nav-search input:focus{outline:none;border-color:var(--link);}.nav-search input::placeholder{color:var(--text-muted);}.search-shortcut{position:absolute;right:8px;top:50%;transform:translateY(-50%);background:var(--bg-secondary);border:1px solid var(--border);border-radius:4px;padding:0.15rem 0.5rem;font-size:0.65rem;color:var(--text-muted);font-family:inherit;pointer-events:none;transition:opacity 0.15s;white-space:nowrap;}.shortcut-divider{opacity:0.5;margin:0 0.1rem;}.nav-search input{padding-right:90px;}.search-dropdown{display:none;position:absolute;top:100%;right:0;width:350px;max-height:400px;overflow-y:auto;background:var(--bg-secondary);border:1px solid var(--border);border-radius:8px;margin-top:0.5rem;box-shadow:0 4px 12px rgba(0,0,0,0.3);z-index:100;}.search-result{display:flex;justify-content:space-between;align-items:center;padding:0.75rem 1rem;color:var(--text);text-decoration:none;border-bottom:1px solid var(--border);}.search-result:last-child{border-bottom:none;}.search-result:hover,.search-result.active{background:var(--bg);}.search-result-name{flex:1;}.search-result-name mark{background:rgba(88,166,255,0.3);color:var(--link);padding:0 2px;border-radius:2px;}.search-result-difficulty{font-size:0.7rem;padding:0.15rem 0.5rem;border-radius:999px;font-weight:600;text-transform:capitalize;margin-left:0.5rem;}.search-result-difficulty.easy{background:rgba(63,185,80,0.2);color:var(--easy);}.search-result-difficulty.medium{background:rgba(210,153,34,0.2);color:var(--medium);}.search-result-difficulty.hard{background:rgba(248,81,73,0.2);color:var(--hard);}main{max-width:1200px;margin:0 auto;padding:2rem;flex:1;width:100%;}footer{background:var(--bg-secondary);border-top:1px solid var(--border);padding:1rem 2rem;text-align:center;color:var(--text-muted);}h1,h2,h3{color:var(--text);margin-bottom:1rem;}h1{font-size:2rem;}h2{font-size:1.5rem;margin-top:2rem;}h3{font-size:1.25rem;}.description{color:var(--text-muted);margin-bottom:2rem;}.filter-bar{display:flex;gap:1rem;margin-bottom:1.5rem;}.filter-bar input,.filter-bar select{padding:0.5rem 1rem;background:var(--bg-secondary);border:1px solid var(--border);border-radius:6px;color:var(--text);font-size:1rem;}.filter-bar input{flex:1;max-width:400px;}.filter-bar input:focus,.filter-bar select:focus{outline:none;border-color:var(--link);}.problems-table{width:100%;border-collapse:collapse;}.problems-table th,.problems-table td{padding:0.75rem 1rem;text-align:left;border-bottom:1px solid var(--border);}.problems-table th{color:var(--text-muted);font-weight:600;font-size:0.875rem;text-transform:uppercase;}.problems-table tr:hover{background:var(--bg-secondary);}.difficulty{display:inline-block;padding:0.25rem 0.75rem;border-radius:999px;font-size:0.75rem;font-weight:600;text-transform:capitalize;}.difficulty.easy{background:rgba(63,185,80,0.2);color:var(--easy);}.difficulty.medium{background:rgba(210,153,34,0.2);color:var(--medium);}.difficulty.hard{background:rgba(248,81,73,0.2);color:var(--hard);}.tags{display:flex;flex-wrap:wrap;gap:0.5rem;}.tag{display:inline-block;padding:0.25rem 0.5rem;background:var(--tag-bg);border-radius:4px;font-size:0.75rem;color:var(--text-muted);}.problem-header{margin-bottom:2rem;}.problem-header .meta{display:flex;align-items:center;gap:1rem;margin:1rem 0;}.leetcode-link{font-size:0.875rem;color:var(--text-muted);}.description-text{background:var(--bg-secondary);padding:1.5rem;border-radius:8px;border:1px solid var(--border);color:var(--text);line-height:1.8;}.description-text p{margin-bottom:1rem;}.description-text p:last-child{margin-bottom:0;}.description-text code{background:var(--bg);padding:0.125rem 0.5rem;border-radius:4px;font-family:'SF Mono','Fira Code',monospace;}.description-text strong{color:var(--link);}.description-text .label{color:var(--text-muted);font-weight:500;}.constraints ul{list-style:disc;padding-left:1.5rem;}.constraints li{padding:0.25rem 0;}.constraints code{background:var(--bg-secondary);padding:0.125rem 0.5rem;border-radius:4px;}.hints details{background:var(--bg-secondary);padding:1rem;border-radius:8px;border:1px solid var(--border);}.hints summary{cursor:pointer;font-weight:600;color:var(--link);}.hints dl{margin-top:1rem;}.hints dt{font-weight:600;color:var(--text-muted);margin-top:1rem;}.hints dd{margin-left:1rem;}.complexity details{background:var(--bg-secondary);border:1px solid var(--border);border-radius:8px;}.complexity summary{padding:1rem;cursor:pointer;font-weight:600;color:var(--link);user-select:none;}.complexity summary:hover{background:rgba(88,166,255,0.1);border-radius:8px;}.complexity details[open] summary{border-radius:8px 8px 0 0;}.complexity ul{list-style:disc;list-style-position:outside;margin:0;padding:1rem;padding-left:2rem;border-top:1px solid var(--border);}.complexity li{padding:0.25rem 0;margin-left:0.5rem;}.complexity code{background:var(--bg-secondary);padding:0.125rem 0.5rem;border-radius:4px;color:var(--link);}.notes details{background:var(--bg-secondary);border:1px solid var(--border);border-radius:8px;}.notes summary{padding:1rem;cursor:pointer;font-weight:600;color:var(--link);user-select:none;}.notes summary:hover{background:rgba(88,166,255,0.1);border-radius:8px;}.notes details[open] summary{border-radius:8px 8px 0 0;}.notes-content{padding:1rem;border-top:1px solid var(--border);font-size:0.9rem;line-height:1.6;}.notes-content p{margin-bottom:1rem;}.notes-content p:last-child{margin-bottom:0;}.notes-content code{background:var(--bg);padding:0.125rem 0.5rem;border-radius:4px;font-family:'SF Mono','Fira Code',monospace;}.notes-content pre{background:var(--bg);padding:1rem;border-radius:6px;overflow-x:auto;margin:1rem 0;}.notes-content pre code{background:none;padding:0;}.notes-content ul,.notes-content ol{margin:1rem 0;padding-left:1.5rem;}.notes-content li{margin-bottom:0.5rem;}.notes-content h1,.notes-content h2,.notes-content h3{margin-top:1.5rem;margin-bottom:0.75rem;}.notes-content h1:first-child,.notes-content h2:first-child,.notes-content h3:first-child{margin-top:0;}.tabs{position:relative;}.tab-buttons{display:flex;gap:0.5rem;margin-bottom:1rem;}.tab-buttons input[type="radio"]{position:absolute;opacity:0;pointer-events:none;}.tab-buttons label{padding:0.5rem 1rem;background:var(--bg-secondary);border:1px solid var(--border);border-radius:6px;color:var(--text-muted);cursor:pointer;font-size:0.875rem;font-weight:600;transition:all 0.2s;}.tab-buttons label:hover{color:var(--text);border-color:var(--text-muted);}.tab-buttons input[type="radio"]:checked+label{background:var(--link);color:var(--bg);border-color:var(--link);}.tab-panels .tab-panel{display:none;}.tab-buttons input:nth-of-type(1):checked~.tab-buttons+.tab-panels .tab-panel:nth-child(1),.tabs:has(input:nth-of-type(1):checked) .tab-panel:nth-child(1){display:block;}.tabs:has(input:nth-of-type(2):checked) .tab-panel:nth-child(2){display:block;}.tabs:has(input:nth-of-type(3):checked) .tab-panel:nth-child(3){display:block;}.tabs:has(input:nth-of-type(4):checked) .tab-panel:nth-child(4){display:block;}.tabs:has(input:nth-of-type(5):checked) .tab-panel:nth-child(5){display:block;}.tabs:has(input:nth-of-type(6):checked) .tab-panel:nth-child(6){display:block;}.tab-panel details{background:var(--bg-secondary);border:1px solid var(--border);border-radius:8px;}.tab-panel summary{padding:1rem;cursor:pointer;font-weight:600;color:var(--link);user-select:none;}.tab-panel summary:hover{background:rgba(88,166,255,0.1);border-radius:8px;}.tab-panel details[open] summary{border-radius:8px 8px 0 0;}.tab-panel pre{margin:0;border-top:1px solid var(--border);border-radius:0 0 8px 8px;overflow-x:auto;}.tab-panel code{font-family:'SF Mono','Fira Code',monospace;font-size:0.875rem;line-height:1.5;}.back-link{margin-top:3rem;padding-top:1rem;border-top:1px solid var(--border);}