/* ═══════════════════════════════════════════════════
   知识答题学习系统
   设计参考: Linear / Vercel - 极简专业风格
   ═══════════════════════════════════════════════════ */

:root {
  --bg: #fafafa;
  --surface: #fff;
  --nav-bg: #111;
  --text: #171717;
  --text-sub: #666;
  --text-muted: #999;
  --line: #eaeaea;
  --line-strong: #d4d4d4;
  --brand: #3b82f6;
  --brand-hover: #2563eb;
  --brand-light: #eff6ff;
  --ok: #059669;
  --ok-bg: #ecfdf5;
  --err: #dc2626;
  --err-bg: #fef2f2;
  --warn: #d97706;
}

/* ══ 暗黑模式 ══ */
[data-theme="dark"] {
  --bg: #1a1b1e;
  --surface: #252628;
  --nav-bg: #161719;
  --text: #e4e4e7;
  --text-sub: #9ca3af;
  --text-muted: #6b7280;
  --line: #36383b;
  --line-strong: #4b4d51;
  --brand: #60a5fa;
  --brand-hover: #93bbfd;
  --brand-light: #1e293b;
  --ok: #34d399;
  --ok-bg: #064e3b;
  --err: #f87171;
  --err-bg: #7f1d1d;
  --warn: #fbbf24;
}
[data-theme="dark"] .card{background:var(--surface);border-color:var(--line)}
[data-theme="dark"] .table th{background:#1f2023}
[data-theme="dark"] .table tbody tr:hover td{background:#2a2b2e}
[data-theme="dark"] .table td{border-color:var(--line)}
[data-theme="dark"] .content-pre{background:#1f2023;border-color:var(--line)}
[data-theme="dark"] .btn{background:var(--surface);color:var(--text)}
[data-theme="dark"] .btn-primary{background:var(--brand);color:#fff}
[data-theme="dark"] input,[data-theme="dark"] select,[data-theme="dark"] textarea{background:var(--surface);color:var(--text);border-color:var(--line-strong)}
[data-theme="dark"] .login-body{background:#111}
[data-theme="dark"] .split-left .table tbody tr:hover td{background:#2a2b2e}
[data-theme="dark"] .split-left .table tbody tr.active td{background:var(--brand-light)}
[data-theme="dark"] .feedback-card.ok{background:var(--ok-bg)}
[data-theme="dark"] .feedback-card.err{background:var(--err-bg)}
[data-theme="dark"] .ds-panel-body pre{background:#111;color:#d4d4d8}

*{box-sizing:border-box;margin:0;padding:0}
body{font-family:"Inter",-apple-system,"PingFang SC","Microsoft YaHei",sans-serif;background:var(--bg);color:var(--text);font-size:14px;line-height:1.6;-webkit-font-smoothing:antialiased}

/* ══ 登录 ══ */
.login-body{display:flex;align-items:center;justify-content:center;min-height:100vh;background:var(--nav-bg)}
.login-wrapper{width:100%;max-width:400px;padding:24px}
.login-card{background:var(--surface);padding:52px 44px 40px;text-align:center;border:1px solid var(--line)}
.login-icon{font-size:52px;display:block;margin-bottom:14px}
.login-brand h1{font-size:20px;font-weight:700;color:var(--text);margin-bottom:6px}
.login-brand p{font-size:13px;color:var(--text-sub);margin-bottom:30px}
.login-form{display:flex;flex-direction:column;gap:14px}
.input-group{display:flex;flex-direction:column;gap:5px}
.input-group label{font-size:12px;font-weight:600;color:var(--text-sub)}
.input-group input{padding:12px 14px;border:1px solid var(--line-strong);font-size:14px;outline:none;transition:border .15s;background:var(--bg)}
.input-group input:focus{border-color:var(--brand);background:#fff}
.login-error{font-size:12px;color:var(--err);min-height:16px;font-weight:500}
.login-submit{display:flex;align-items:center;justify-content:center;gap:6px;padding:13px;background:var(--brand);color:#fff;border:none;font-size:14px;font-weight:600;cursor:pointer;transition:background .15s;font-family:inherit}
.login-submit:hover{background:var(--brand-hover)}

/* ══ 顶部导航 ══ */
.topnav{background:var(--nav-bg);position:sticky;top:0;z-index:100;border-bottom:1px solid rgba(255,255,255,.06)}
.topnav-inner{display:flex;align-items:center;padding:0 28px;height:52px;gap:2px}
.topnav-brand{font-size:15px;font-weight:650;color:#fff;text-decoration:none;margin-right:24px;white-space:nowrap;letter-spacing:-.3px;opacity:.85}
.topnav-brand:hover{opacity:1}
.topnav-links{display:flex;align-items:center;gap:1px;flex:1;overflow-x:auto}
.topnav-links a{padding:6px 14px;font-size:13px;font-weight:450;color:#888;text-decoration:none;cursor:pointer;white-space:nowrap;transition:all .12s}
.topnav-links a:hover{color:#ccc}
.topnav-links a.active{color:#fff;font-weight:550}
.topnav-right{margin-left:auto}
.topnav-logout{padding:6px 12px;font-size:13px;font-weight:450;color:#888;text-decoration:none;transition:color .12s}
.topnav-logout:hover{color:#ccc}

/* ══ 主内容 ══ */
.main-content{padding:24px 28px}

.page-panel{display:none}
.page-panel.active{display:block}
.page-title{font-size:26px;font-weight:700;margin-bottom:28px;letter-spacing:-.6px}

/* ══ 卡片 ══ */
.card{background:var(--surface);border:1px solid var(--line);padding:24px 28px;margin-bottom:12px}

/* ══ 统计卡片 ══ */
.stats-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(180px,1fr));gap:12px;margin-bottom:20px}
.stat-card{background:var(--surface);border:1px solid var(--line);padding:26px 20px;text-align:center;cursor:pointer;transition:all .12s}
.stat-card:hover{border-color:var(--brand);background:var(--brand-light)}
.stat-num{font-size:36px;font-weight:750;color:var(--brand);line-height:1;letter-spacing:-1px}
.stat-label{font-size:13px;color:var(--text-sub);margin-top:6px;font-weight:450}

/* ══ 网格 ══ */
.grid-2{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.grid-auto{display:flex;flex-wrap:wrap;gap:8px;align-items:center}
@media(max-width:800px){.grid-2{grid-template-columns:1fr}}

/* ══ 按钮 ══ */
.btn{display:inline-flex;align-items:center;gap:5px;padding:7px 16px;border:1px solid var(--line-strong);background:var(--surface);color:var(--text);font-size:13px;font-weight:500;cursor:pointer;transition:all .12s;text-decoration:none;font-family:inherit}
.btn:hover{border-color:var(--text-sub)}
.btn-primary{background:var(--text);border-color:var(--text);color:#fff}
.btn-primary:hover{background:#000;border-color:#000;color:#fff}
.btn-sm{padding:4px 12px;font-size:12px}
.btn:disabled{opacity:.35;cursor:default}

/* ══ 输入框 ══ */
input,select,textarea{border:1px solid var(--line-strong);padding:9px 14px;font-size:14px;background:var(--bg);color:var(--text);outline:none;font-family:inherit;transition:border .15s}
input:focus,select:focus,textarea:focus{border-color:var(--text);background:#fff}
textarea{resize:vertical;min-height:100px}

/* ══ 文字 ══ */
.muted{color:var(--text-sub)} .muted-light{color:var(--text-muted)}
.text-sm{font-size:13px} .text-lg{font-size:16px;font-weight:600}
.mt-8{margin-top:8px} .mt-12{margin-top:12px} .mt-16{margin-top:16px}
.mb-8{margin-bottom:8px} .mb-12{margin-bottom:12px} .mb-16{margin-bottom:16px}

/* ══ 徽章 ══ */
.badge{display:inline-block;padding:2px 10px;font-size:11px;font-weight:500;border:1px solid var(--line);color:var(--text-sub);line-height:1.6}
.badge-brand{border-color:transparent;background:var(--brand-light);color:var(--brand)}
.badge-ok{border-color:transparent;background:var(--ok-bg);color:var(--ok)}
.badge.clickable{cursor:pointer;transition:all .12s}
.badge.clickable:hover{background:var(--text);border-color:var(--text);color:#fff}

/* ══ 表格 ══ */
.table-wrap{overflow-x:auto}
.table{width:100%;border-collapse:collapse;font-size:13px}
.table th,.table td{text-align:left;padding:10px 16px;border-bottom:1px solid var(--line)}
.table th{font-weight:500;color:var(--text-muted);font-size:12px;padding-top:8px;padding-bottom:10px}
.table tbody tr td{padding-top:14px;padding-bottom:14px}
.table tbody tr:hover td{background:var(--bg)}
tr.clickable-row{cursor:pointer}
.clickable-link{color:var(--text);font-weight:500}
.clickable-link:hover{color:var(--brand)}

/* ══ 答题选项 ══ */
.option-block{display:block;width:100%;padding:14px 18px;border:1px solid var(--line);margin-bottom:8px;background:var(--surface);cursor:pointer;text-align:left;font-size:14px;line-height:1.5;transition:all .12s}
.option-block:hover{border-color:var(--text-sub)}
.option-block.selected{border-color:var(--text);background:var(--bg)}
.option-block.correct{border-color:var(--ok)}
.option-block.wrong{border-color:var(--err)}
.option-block .key{display:inline-block;width:26px;height:26px;line-height:26px;text-align:center;background:var(--bg);font-weight:600;font-size:12px;margin-right:10px;color:var(--text-sub)}
.option-block.correct .key{background:var(--ok);color:#fff}
.option-block.wrong .key{background:var(--err);color:#fff}
.option-block.selected .key{background:var(--text);color:#fff}

/* ══ 反馈 ══ */
.feedback-card{padding:16px 20px;margin-top:10px;border:1px solid var(--line)}
.feedback-card.ok{border-color:var(--ok);background:var(--ok-bg)}
.feedback-card.err{border-color:var(--err);background:var(--err-bg)}

/* ══ 加载 ══ */
.spinner{display:inline-block;width:18px;height:18px;border:2px solid var(--line);border-top-color:var(--text);animation:spin .6s linear infinite}
@keyframes spin{to{transform:rotate(360deg)}}

/* ══ 内联按钮 ══ */
.ds-btn{display:inline-flex;align-items:center;gap:3px;padding:2px 10px;border:1px solid var(--line);font-size:11px;font-weight:500;background:var(--surface);color:var(--text-sub);cursor:pointer;transition:all .12s;text-decoration:none;font-family:inherit}
.ds-btn:hover{border-color:var(--text-sub);color:var(--text)}

/* ══ DeepSeek 查询浮窗 ══ */
.ds-panel{position:fixed;right:24px;top:76px;width:440px;max-height:80vh;background:var(--surface);border:1px solid var(--line-strong);z-index:9999;display:flex;flex-direction:column;overflow:hidden}
.ds-panel-header{display:flex;justify-content:space-between;align-items:center;padding:14px 18px;background:var(--nav-bg);color:#fff;font-weight:600;font-size:13px}
.ds-panel-header .btn{color:#fff;border-color:rgba(255,255,255,.15)}
.ds-panel-header .btn:hover{background:rgba(255,255,255,.08)}
.ds-panel-body{padding:18px;overflow-y:auto;font-size:13px;line-height:1.75;color:var(--text)}
.ds-panel-body p{margin-bottom:10px}
.ds-panel-body h3{font-size:15px;margin:14px 0 8px;font-weight:600}
.ds-panel-body code{background:var(--bg);padding:1px 5px;font-size:12px;color:var(--brand)}
.ds-panel-body pre{white-space:pre-wrap;font-size:12px;background:var(--nav-bg);color:#ccc;padding:14px;overflow-x:auto;line-height:1.6}
.ds-panel-body ul{margin:6px 0 10px 18px}
.ds-panel-body li{margin-bottom:3px}

/* ══ 分页 ══ */
.pager{display:flex;align-items:center;gap:10px;margin:16px 0;font-size:13px;color:var(--text-sub);font-weight:500}

/* ══ 内容区块 ══ */
pre{font-family:"SF Mono","Consolas","Microsoft YaHei",monospace}
.content-pre{white-space:pre-wrap;font-size:13px;line-height:1.7;color:var(--text-sub);max-height:400px;overflow-y:auto;padding:18px;background:var(--bg);border-left:2px solid var(--line-strong)}
.content-pre table{border-collapse:collapse;width:100%;margin:8px 0;white-space:normal}
.content-pre td,.content-pre th{border:1px solid var(--line);padding:6px 10px;font-size:13px}
.content-pre th{background:var(--bg);font-weight:600}
.content-pre img{max-width:100%}

/* ══ 空状态 ══ */
.empty-state{text-align:center;padding:48px 20px;color:var(--text-muted)}

/* ══ 分栏布局 ══ */
.split-layout{display:flex;gap:12px;align-items:flex-start}
.split-left{width:520px;flex-shrink:0;overflow-y:auto;max-height:calc(100vh - 120px);position:sticky;top:70px}
.split-right{flex:1;overflow-y:auto}
.split-left .table{font-size:13px;table-layout:fixed;width:100%}
.split-left .table td{padding:9px 14px}
.split-left .table td:first-child,.split-left .table th:first-child{word-break:break-word;width:100%}
.split-left .table td:nth-child(2),.split-left .table th:nth-child(2){white-space:nowrap}
.split-left .table td:last-child,.split-left .table th:last-child{width:40px}
.split-left .table tbody tr{cursor:pointer;border-left:3px solid transparent}
.split-left .table tbody tr:hover td{background:var(--bg)}
.split-left .table tbody tr.active td{background:var(--brand-light);font-weight:600}
.split-left .table tbody tr.active{border-left-color:var(--brand)}
@media(max-width:900px){.split-layout{grid-template-columns:1fr}.split-left{position:static;max-height:250px}}

/* ══ LeetCode ══ */
.lc-layout{display:flex;gap:12px;align-items:flex-start}
.lc-left{flex:1;min-width:0;max-height:calc(100vh - 120px);overflow-y:auto}
.lc-right{width:55%;min-width:480px}
.lc-desc{font-size:14px;line-height:1.8;color:var(--text)}
.lc-desc pre{background:var(--bg);padding:12px 16px;overflow-x:auto;font-size:13px;border:1px solid var(--line);margin:8px 0}
.lc-desc code{background:var(--bg);padding:1px 5px;font-size:12px}
.lc-desc h3{margin:16px 0 8px;font-size:15px;font-weight:600}
.lc-desc h4{margin:12px 0 6px;font-size:14px;font-weight:600}
.lc-desc ul,.lc-desc ol{margin:6px 0 10px 18px}
.lc-desc li{margin-bottom:3px}
.lc-desc table{border-collapse:collapse;width:100%;margin:8px 0}
.lc-desc td,.lc-desc th{border:1px solid var(--line);padding:6px 10px;font-size:13px}
.lc-desc th{background:var(--bg);font-weight:600}
.diff-easy{color:#059669;font-weight:600}
.diff-medium{color:#d97706;font-weight:600}
.diff-hard{color:#dc2626;font-weight:600}
#lcCodeEditor{width:100%;font-family:'SF Mono','Consolas',monospace;font-size:13px;resize:vertical;tab-size:4;background:var(--bg);border:1px solid var(--line-strong);color:var(--text);padding:12px;line-height:1.6;box-sizing:border-box;background-image:linear-gradient(to right,rgba(128,128,128,.06) 1px,transparent 1px);background-size:8px 100%}
#lcCodeEditor{position:relative;z-index:2;background:transparent;caret-color:var(--text)}
#lcCodeEditor:focus{outline:none}
.lc-overlay{position:absolute;top:0;left:0;right:0;bottom:0;margin:0;padding:12px;font-family:'SF Mono','Consolas',monospace;font-size:13px;line-height:1.6;tab-size:4;color:transparent;white-space:pre;overflow:hidden;pointer-events:none;z-index:1;word-wrap:normal}
.lc-overlay .sp{color:transparent}
.lc-overlay .sp::before{content:'·';color:rgba(128,128,128,.25)}
.lc-overlay .tb{color:transparent}
.lc-overlay .tb::before{content:'→  ';color:rgba(128,128,128,.18)}
/* ══ VS Code-style Sandbox ══ */
.sb-titlebar{display:flex;justify-content:space-between;align-items:center;background:#252526;padding:0 12px;height:36px;border:1px solid var(--line-strong);border-bottom:none}
.sb-titlebar-text{font-size:12px;color:#999}
.sb-tabs{display:flex;gap:0}
.sb-tab{background:transparent;border:none;color:#999;padding:6px 16px;font-size:12px;cursor:pointer;border-bottom:2px solid transparent;transition:all .15s}
.sb-tab:hover{color:#ddd}
.sb-tab.active{color:#fff;border-bottom-color:var(--brand)}
.sb-editor-wrap{display:flex;border:1px solid var(--line-strong);border-top:none;background:#1e1e1e;overflow:hidden}
.sb-gutter{width:44px;background:#1e1e1e;padding:12px 0;text-align:right;font-family:'SF Mono','Consolas',monospace;font-size:13px;line-height:1.6;color:#858585;user-select:none;overflow:hidden;border-right:1px solid #333;flex-shrink:0}
.sb-gutter span{display:block;padding-right:10px}
.sb-editor-container{flex:1;position:relative;min-height:360px}
.sb-overlay{position:absolute;top:0;left:0;right:0;bottom:0;margin:0;padding:12px 16px;font-family:'SF Mono','Consolas',monospace;font-size:13px;line-height:1.6;tab-size:4;color:transparent;white-space:pre;overflow:auto;pointer-events:none;z-index:1;word-wrap:normal}
.sb-overlay .sp{color:rgba(255,255,255,.12)}
.sb-overlay .sp::before{content:'·';color:rgba(255,255,255,.18)}
.sb-overlay .tb{color:rgba(255,255,255,.1)}
.sb-overlay .tb::before{content:'→  ';color:rgba(255,255,255,.12)}
.sb-editor-wrap textarea{position:relative;z-index:2;width:100%;height:100%;min-height:360px;border:none;outline:none;resize:none;padding:12px 16px;font-family:'SF Mono','Consolas',monospace;font-size:13px;line-height:1.6;tab-size:4;color:#d4d4d4;background:transparent;white-space:pre;overflow:auto;caret-color:#fff}
.sb-editor-wrap textarea::placeholder{color:#555}
.sb-editor-wrap textarea:focus{outline:none;border:none}
.sb-statusbar{display:flex;justify-content:space-between;align-items:center;background:#007acc;color:#fff;padding:0 12px;height:28px;font-size:12px}
.sb-statusbar-right{display:flex;gap:6px;align-items:center}
.sb-terminal{margin-top:1px;border:1px solid var(--line-strong)}
.sb-terminal-bar{display:flex;justify-content:space-between;align-items:center;background:#252526;padding:4px 12px;font-size:12px;color:#999;border-bottom:1px solid var(--line-strong)}
.sb-terminal pre{background:#1e1e1e;color:#d4d4d4;padding:12px 16px;overflow:auto;font-size:13px;max-height:300px;white-space:pre-wrap;margin:0;font-family:'SF Mono','Consolas',monospace}
.lc-result-ok{border-color:var(--ok)!important;background:var(--ok-bg)!important}
.lc-result-err{border-color:var(--err)!important;background:var(--err-bg)!important}
@media(max-width:1000px){.lc-layout{flex-direction:column}.lc-right{width:100%;min-width:0}}
/* ══ Notes ══ */
.notes-layout{display:flex;gap:12px;align-items:flex-start}
.notes-sidebar{width:220px;flex-shrink:0;max-height:calc(100vh - 120px);overflow-y:auto}
.notes-editor{flex:1;min-width:0}
/* Folder styles */
.notes-folders{margin-bottom:4px;}
.notes-folder-item{padding:4px 8px;cursor:pointer;border-radius:4px;display:flex;justify-content:space-between;align-items:center;font-size:12px;margin-bottom:1px;}
.notes-folder-item:hover{background:var(--bg);}
.notes-folder-item.active{background:var(--brand-light);font-weight:600;}
.notes-folder-badge{font-size:10px;color:var(--muted);background:var(--bg);padding:0 4px;border-radius:8px;}
.notes-folder-actions{margin-bottom:8px;display:flex;gap:4px;}
.notes-item{padding:6px;cursor:pointer;border-left:3px solid transparent;margin-bottom:2px;font-size:13px;display:flex;align-items:center;justify-content:space-between}
.notes-item:hover{background:var(--bg)}
.notes-item.active{background:var(--brand-light);border-left-color:var(--brand);font-weight:600}
.notes-item .muted{font-size:11px;display:block}
.notes-toolbar{display:flex;gap:2px;padding:4px 8px;background:var(--bg);border:1px solid var(--line-strong);border-bottom:none;flex-wrap:wrap;align-items:center}
.notes-tb-btn{background:transparent;border:none;color:var(--text);padding:4px 8px;cursor:pointer;font-size:12px;border-radius:3px;min-width:24px;text-align:center}
.notes-tb-btn:hover{background:var(--line)}
.notes-tb-btn.active{background:var(--brand);color:#fff}
.notes-statusbar{display:flex;justify-content:space-between;align-items:center;padding:6px 8px;background:var(--bg);border:1px solid var(--line-strong);border-top:none;font-size:12px}
.notes-preview{font-size:14px;line-height:1.8;padding:12px;overflow-y:auto;border:1px solid var(--line-strong);border-top:none;white-space:normal}
.notes-preview h2,.notes-preview h3,.notes-preview h4{margin:12px 0 6px}
.notes-preview pre{background:var(--bg);padding:10px;overflow-x:auto;font-size:13px}
.notes-preview code{background:var(--bg);padding:1px 4px;font-size:12px}
.notes-preview ul,.notes-preview ol{margin:6px 0 10px 20px}
.notes-preview blockquote{border-left:3px solid var(--brand);padding:4px 12px;margin:8px 0;color:var(--text-sub)}
.notes-preview table{border-collapse:collapse;width:100%;margin:8px 0}
.notes-preview td,.notes-preview th{border:1px solid var(--line);padding:6px 10px;font-size:13px}
.notes-preview th{background:var(--bg);font-weight:600}
.notes-preview img{max-width:100%}
.notes-preview input[type=checkbox]{margin-right:6px;transform:scale(1.2)}
.notes-fullscreen{position:fixed!important;top:0;left:0;right:0;bottom:0;z-index:998;background:var(--surface);padding:20px;overflow-y:auto}
.notes-fullscreen textarea{min-height:calc(100vh - 160px)!important}
.notes-fullscreen .notes-preview{min-height:calc(100vh - 160px)!important}
@media(max-width:700px){.notes-layout{flex-direction:column}.notes-sidebar{width:100%;max-height:200px}}