/* styles.css */
:root{
  --bg: #eaf5ff;
  --card: #ffffff;
  --ink: #0b1b2a;
  --muted: #274760;
  --border: #9dc7f0;
  --accent: #2b6cb0;
  --accent2: #1e4f85;
  --shadow: rgba(0,0,0,0.08);
}

*{ box-sizing: border-box; }

body{
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: linear-gradient(180deg, var(--bg), #f7fbff);
  color: var(--ink);
}

.container{
  width: min(1020px, 92vw);
  margin: 0 auto;
}

.header{
  padding: 22px 0 18px;
  border-bottom: 3px solid var(--border);
  background: linear-gradient(180deg, #dff0ff, #eff8ff);
}

h1, h2, h3, h4, p, li, th, td, button{
  font-weight: 700;
}

h1{
  margin: 0 0 6px;
  font-size: 30px;
  letter-spacing: 0.2px;
}

.subtitle{
  margin: 0 0 14px;
  color: var(--muted);
  font-size: 14px;
}

.actions{
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.btn{
  border: 2px solid var(--accent);
  background: var(--accent);
  color: #fff;
  padding: 10px 12px;
  border-radius: 12px;
  cursor: pointer;
  box-shadow: 0 8px 18px var(--shadow);
  transition: transform 0.08s ease, background 0.2s ease;
}

.btn:hover{ background: var(--accent2); }
.btn:active{ transform: translateY(1px); }

.btn-outline{
  background: #ffffff;
  color: var(--accent2);
  border-color: var(--border);
}

main{ padding: 18px 0 40px; }

.card{
  background: var(--card);
  border: 2px solid var(--border);
  border-radius: 18px;
  padding: 16px 16px;
  box-shadow: 0 10px 22px var(--shadow);
  margin: 14px 0;
}

.highlight{
  background: linear-gradient(180deg, #ffffff, #f3fbff);
  border-color: #7fb7ef;
}

.nav-grid{
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 10px;
}

.nav-btn{
  border: 2px solid var(--border);
  background: #f4fbff;
  color: var(--accent2);
  padding: 12px 12px;
  border-radius: 14px;
  cursor: pointer;
  box-shadow: 0 8px 16px var(--shadow);
  transition: transform 0.08s ease, background 0.2s ease;
}

.nav-btn:hover{ background: #e8f5ff; }
.nav-btn:active{ transform: translateY(1px); }

.section-head{
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
  border-bottom: 2px dashed var(--border);
  padding-bottom: 10px;
  margin-bottom: 10px;
}

.toggle{
  border: 2px solid var(--border);
  background: #f4fbff;
  color: var(--accent2);
  padding: 8px 10px;
  border-radius: 12px;
  cursor: pointer;
}

.section-body{ padding-top: 2px; }

ul{
  margin: 8px 0 8px 18px;
  color: var(--ink);
}

li{
  margin: 8px 0;
  line-height: 1.35;
}

.example{
  border: 2px solid #cfe7fb;
  background: #f7fcff;
  border-radius: 14px;
  padding: 12px;
  margin-top: 10px;
}

.note{
  color: var(--muted);
  margin-top: 10px;
  border-left: 6px solid var(--border);
  padding: 10px 12px;
  background: #f7fcff;
  border-radius: 12px;
}

.table-wrap{
  overflow: auto;
  border: 2px solid #cfe7fb;
  border-radius: 14px;
  background: #f7fcff;
}

table{
  width: 100%;
  border-collapse: collapse;
  min-width: 740px;
}

th, td{
  border-bottom: 2px solid #d6ecff;
  text-align: left;
  padding: 12px;
  vertical-align: top;
}

th{
  background: #eaf6ff;
  color: var(--accent2);
}

.footer{
  margin-top: 20px;
  border-top: 3px solid var(--border);
  padding-top: 10px;
  color: var(--muted);
}

.backtop{
  position: fixed;
  right: 16px;
  bottom: 16px;
  width: 44px;
  height: 44px;
  border-radius: 999px;
  border: 2px solid var(--border);
  background: #ffffff;
  color: var(--accent2);
  cursor: pointer;
  box-shadow: 0 12px 26px var(--shadow);
  display: none;
}

@media (max-width: 720px){
  .nav-grid{ grid-template-columns: 1fr; }
  h1{ font-size: 24px; }
}
@media print{
  .actions, .backtop, .toggle{ display: none !important; }
  body{ background: #fff; }
  .card{ box-shadow: none; }
}