/* ============ 数学可视化工具 · 现代深色主题 ============ */
:root {
  --bg: #0d1117;
  --bg2: #161b22;
  --panel: #161b22;
  --panel2: #1c2129;
  --border: #30363d;
  --border2: #3d444d;
  --text: #e6edf3;
  --muted: #8b949e;
  --accent: #58a6ff;
  --accent2: #79c0ff;
  --success: #3fb950;
  --warn: #d29922;
  --danger: #f85149;
  --radius: 10px;
  --shadow: 0 4px 16px rgba(0, 0, 0, .35);
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html, body { height: 100%; }
body {
  font-family: "Segoe UI", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent2); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- 顶栏 ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; gap: 18px;
  padding: 0 26px; height: 56px;
  background: rgba(13, 17, 23, .82);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; font-size: 16px; white-space: nowrap; }
.brand .logo { display: inline-flex; }
.brand small { color: var(--muted); font-weight: 400; font-size: 11px; }
.badge {
  font-size: 10px; color: var(--muted); border: 1px solid var(--border2);
  padding: 2px 8px; border-radius: 20px; letter-spacing: .6px; white-space: nowrap;
}
.topbar nav { display: flex; gap: 2px; margin-left: 8px; }
.topbar nav a {
  color: var(--muted); padding: 6px 13px; border-radius: 7px;
  transition: .15s; font-size: 13.5px; white-space: nowrap;
}
.topbar nav a:hover { color: var(--text); background: var(--panel2); text-decoration: none; }
.topbar nav a.active { color: #fff; background: var(--panel2); box-shadow: inset 0 -2px 0 var(--accent); }
.top-actions { margin-left: auto; display: flex; align-items: center; gap: 8px; }
.user-area { display: flex; align-items: center; gap: 10px; }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex; align-items: center; gap: 6px;
  border: 1px solid var(--border2); background: var(--panel2); color: var(--text);
  padding: 6px 14px; border-radius: 7px; cursor: pointer; font-size: 13px;
  transition: .15s; white-space: nowrap;
}
.btn:hover { border-color: var(--accent); background: #21262d; }
.btn.primary { background: #238636; border-color: rgba(240, 246, 252, .1); color: #fff; font-weight: 600; }
.btn.primary:hover { background: #2ea043; border-color: rgba(240, 246, 252, .1); }
.btn.ghost { background: transparent; }
.btn.danger:hover { border-color: var(--danger); color: var(--danger); background: rgba(248, 81, 73, .08); }
.btn.small { padding: 3px 10px; font-size: 12px; }
.btn:disabled { opacity: .45; cursor: not-allowed; }

/* ---------- 输入控件 ---------- */
input, select, textarea, button { font-family: inherit; }
input[type=text], input[type=number], input[type=password], select, textarea {
  background: var(--bg2); border: 1px solid var(--border2); color: var(--text);
  border-radius: 7px; padding: 6px 10px; font-size: 13px; width: 100%;
}
input:focus, select:focus, textarea:focus { outline: 2px solid rgba(88, 166, 255, .35); border-color: var(--accent); }
input[type=range] { width: 100%; accent-color: var(--accent); }
label.field { display: block; margin-bottom: 12px; }
label.field > span { display: block; font-size: 12px; color: var(--muted); margin-bottom: 5px; }
.row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.grow { flex: 1; min-width: 0; }

/* ---------- 布局 ---------- */
.container { max-width: 1200px; margin: 0 auto; padding: 28px; }
.page { display: grid; grid-template-columns: 340px 1fr; gap: 18px; padding: 18px 22px; max-width: 1500px; margin: 0 auto; align-items: start; }
.panel {
  background: var(--panel); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px 18px;
}
.panel h3 { font-size: 13.5px; margin-bottom: 12px; color: var(--text); display: flex; align-items: center; gap: 8px; font-weight: 600; }
.panel h3 .n { background: var(--accent); color: #0d1117; width: 20px; height: 20px; border-radius: 50%; display: inline-flex; align-items: center; justify-content: center; font-size: 11px; font-weight: 700; }
.sidebar { display: flex; flex-direction: column; gap: 14px; position: sticky; top: 70px; max-height: calc(100vh - 90px); overflow-y: auto; padding-right: 4px; }
.main { min-width: 0; display: flex; flex-direction: column; gap: 14px; }
.plot-box { width: 100%; }
.plot-box .plot { width: 100%; height: 460px; }

/* ---------- 矩阵 ---------- */
.matrix-wrap { overflow-x: auto; margin: 6px 0; }
.matrix { display: inline-block; border-collapse: collapse; border-left: 2px solid var(--text); border-right: 2px solid var(--text); }
.matrix td { padding: 4px 7px; text-align: center; min-width: 44px; }
.matrix input {
  width: 62px; text-align: center; background: transparent; border: 1px solid transparent;
  padding: 4px; border-radius: 5px; font-size: 13px;
}
.matrix input:hover { border-color: var(--border2); }
.matrix input:focus { border-color: var(--accent); outline: none; background: var(--bg2); }
.matrix-result td { padding: 5px 9px; font-family: Consolas, monospace; font-size: 13px; }

/* ---------- 公式 ---------- */
.math { padding: 8px 0; overflow-x: auto; }
.katex { font-size: 1.02em; }
.metric-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 8px; }
.metric { background: var(--bg2); border: 1px solid var(--border); border-radius: 7px; padding: 8px 10px; }
.metric .k { font-size: 11px; color: var(--muted); }
.metric .v { font-family: Consolas, monospace; font-size: 14px; margin-top: 2px; word-break: break-all; }

/* ---------- 选项卡 ---------- */
.tabs { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 12px; }
.tab { padding: 5px 12px; border-radius: 7px; border: 1px solid var(--border2); background: transparent; color: var(--muted); cursor: pointer; font-size: 12.5px; transition: .15s; }
.tab:hover { color: var(--text); border-color: var(--accent); }
.tab.active { background: rgba(88, 166, 255, .15); border-color: var(--accent); color: #fff; }

/* ---------- 提示 / 弹窗 ---------- */
#toast-box { position: fixed; top: 64px; right: 16px; z-index: 999; display: flex; flex-direction: column; gap: 8px; }
.toast {
  padding: 9px 15px; border-radius: 8px; background: var(--panel2);
  border: 1px solid var(--border2); font-size: 13px; animation: slideIn .18s ease; max-width: 340px;
  box-shadow: var(--shadow);
}
.toast.success { border-color: var(--success); }
.toast.error { border-color: var(--danger); }
@keyframes slideIn { from { transform: translateX(30px); opacity: 0; } to { transform: none; opacity: 1; } }

.modal-mask {
  position: fixed; inset: 0; background: rgba(1, 4, 9, .75); z-index: 200;
  display: flex; align-items: center; justify-content: center; padding: 20px;
  backdrop-filter: blur(4px);
}
.modal {
  background: var(--panel); border: 1px solid var(--border2); border-radius: 12px;
  width: 460px; max-width: 100%; max-height: 86vh; overflow-y: auto; padding: 22px;
  box-shadow: var(--shadow);
}
.modal h3 { margin-bottom: 14px; }
.modal .close { float: right; background: none; border: none; color: var(--muted); font-size: 20px; cursor: pointer; }
.list-item {
  display: flex; align-items: center; gap: 10px; padding: 9px; border: 1px solid var(--border2);
  border-radius: 8px; margin-bottom: 8px; background: var(--bg2);
}
.list-item .meta { flex: 1; min-width: 0; }
.list-item .meta .t { font-weight: 600; font-size: 13px; }
.list-item .meta .d { color: var(--muted); font-size: 11px; }
.empty { color: var(--muted); text-align: center; padding: 16px; }

/* ---------- 首页 ---------- */
.hero {
  padding: 64px 24px 30px; text-align: center;
  background:
    radial-gradient(600px 260px at 50% -60px, rgba(88, 166, 255, .14), transparent 70%);
}
.hero h1 {
  font-size: 34px; letter-spacing: .5px; font-weight: 800;
  background: linear-gradient(90deg, #e6edf3 30%, #79c0ff);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero p { color: var(--muted); max-width: 660px; margin: 14px auto 0; font-size: 14.5px; }
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 16px; max-width: 1120px; margin: 30px auto 0; padding: 0 24px; }
.card {
  background: var(--panel); border: 1px solid var(--border); border-radius: 12px;
  padding: 22px; transition: .18s; display: block; color: var(--text);
}
.card:hover { transform: translateY(-3px); border-color: var(--accent); box-shadow: var(--shadow); text-decoration: none; }
.card .icon { width: 40px; height: 40px; margin-bottom: 12px; color: var(--accent); }
.card h2 { margin: 0 0 6px; font-size: 18px; }
.card .desc { color: var(--muted); font-size: 13px; margin-bottom: 8px; }
.card .feats { list-style: none; margin-top: 8px; }
.card .feats li { color: var(--muted); font-size: 12.5px; padding: 2px 0; }
.card .feats li::before { content: "› "; color: var(--accent); font-weight: 700; }
.feature-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; max-width: 1120px; margin: 30px auto 0; padding: 0 24px; }
.feature { background: var(--bg2); border: 1px solid var(--border); border-radius: 10px; padding: 14px 16px; }
.feature h3 { color: var(--text); font-size: 13.5px; margin-bottom: 5px; }
.feature p { color: var(--muted); font-size: 12.5px; }
footer { text-align: center; color: var(--muted); font-size: 12px; padding: 30px 20px; border-top: 1px solid var(--border); margin-top: 36px; }
footer .credit { color: var(--text); font-weight: 600; margin-bottom: 4px; letter-spacing: .5px; }

/* ---------- 公式卡片 ---------- */
.formula-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(340px, 1fr)); gap: 14px; }
.fcard { background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 16px 18px; }
.fcard h3 { font-size: 13.5px; margin-bottom: 8px; color: var(--text); }
.fcard .math { font-size: 1.05em; }
.fcard p { color: var(--muted); font-size: 12px; margin-top: 8px; }
.fcard .tag { font-size: 10px; color: var(--muted); border: 1px solid var(--border2); border-radius: 12px; padding: 1px 8px; margin-left: 6px; font-weight: 400; }

/* ---------- 响应式 ---------- */
@media (max-width: 900px) {
  .page { grid-template-columns: 1fr; padding: 12px; }
  .sidebar { position: static; max-height: none; }
  .hero h1 { font-size: 24px; }
  .topbar { flex-wrap: wrap; height: auto; padding: 10px 14px; gap: 8px; }
}