:root {
  --color-bg: #f7f8fa;
  --color-surface: #ffffff;
  --color-border: #e5e7eb;
  --color-text: #1f2937;
  --color-text-muted: #6b7280;
  --color-primary: #0f766e;
  --color-primary-soft: #ecfdf5;
  --color-primary-dark: #0b5a55;
  --color-accent: #f59e0b;
  --color-danger: #dc2626;
  --color-warning-bg: #fef3c7;
  --color-info: #1d4ed8;
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.04), 0 1px 3px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 4px 12px rgba(15, 23, 42, 0.08);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --sidebar-w: 260px;
  --topbar-h: 64px;
  --max-content: 920px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: 'Pretendard', 'Malgun Gothic', -apple-system, BlinkMacSystemFont, system-ui, sans-serif;
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; height: auto; }

/* Layout */
.app {
  min-height: 100vh;
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  grid-template-rows: auto 1fr auto;
  grid-template-areas:
    "sidebar topbar"
    "sidebar main"
    "sidebar footer";
}

/* Topbar */
.topbar {
  grid-area: topbar;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 0 28px;
  height: var(--topbar-h);
  position: sticky;
  top: 0;
  z-index: 30;
}
.topbar-title {
  font-size: 17px;
  font-weight: 700;
  letter-spacing: -0.01em;
}
.topbar-notice {
  flex: 1;
  font-size: 13px;
  color: var(--color-text-muted);
  line-height: 1.45;
}
.topbar-notice .danger { color: var(--color-danger); font-weight: 700; }
.menu-toggle {
  display: none;
  border: 1px solid var(--color-border);
  background: var(--color-surface);
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  align-items: center;
  justify-content: center;
  padding: 0;
}
.menu-toggle span {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--color-text);
  position: relative;
}
.menu-toggle span::before,
.menu-toggle span::after {
  content: "";
  position: absolute;
  left: 0;
  width: 18px;
  height: 2px;
  background: var(--color-text);
}
.menu-toggle span::before { top: -6px; }
.menu-toggle span::after  { top: 6px; }

/* Sidebar */
.sidebar {
  grid-area: sidebar;
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  padding: 24px 14px;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
}
.sidebar-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 4px 10px 18px;
  border-bottom: 1px solid var(--color-border);
  margin-bottom: 12px;
}
.sidebar-brand .logo {
  width: 36px;
  height: 36px;
  border-radius: 8px;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  color: #fff;
  display: grid;
  place-items: center;
  font-weight: 800;
  font-size: 10px;
  letter-spacing: -0.02em;
  flex-shrink: 0;
}
.sidebar-brand .name {
  font-size: 14px;
  font-weight: 700;
  letter-spacing: -0.01em;
}
.sidebar-brand .sub {
  font-size: 11px;
  color: var(--color-text-muted);
}

.nav-group-label {
  padding: 12px 12px 6px;
  font-size: 11px;
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.nav-list {
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-list a {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 12px;
  color: var(--color-text);
  font-size: 14px;
  border-radius: var(--radius-sm);
  margin-bottom: 2px;
  transition: background-color .15s ease, color .15s ease;
}
.nav-list a:hover {
  background: var(--color-bg);
  text-decoration: none;
}
.nav-list a.active {
  background: var(--color-primary-soft);
  color: var(--color-primary-dark);
  font-weight: 600;
}
.nav-list a .dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-border);
  flex-shrink: 0;
}
.nav-list a.active .dot {
  background: var(--color-primary);
}

/* Main / Article */
.main {
  grid-area: main;
  padding: 32px 28px 48px;
}
.article {
  max-width: var(--max-content);
  margin: 0;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 36px 40px;
  box-shadow: var(--shadow-sm);
}
.article-title {
  font-size: 22px;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin: 0 0 6px;
}
.article-subtitle {
  margin: 0 0 24px;
  color: var(--color-text-muted);
  font-size: 14px;
}

.article h3 {
  font-size: 16px;
  font-weight: 700;
  margin: 28px 0 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--color-border);
}
.article h4 {
  font-size: 15px;
  font-weight: 700;
  margin: 22px 0 10px;
}
.article p { margin: 0 0 12px; }
.article hr {
  border: 0;
  border-top: 1px dashed var(--color-border);
  margin: 24px 0;
}

.badge {
  display: inline-block;
  background: var(--color-primary-soft);
  color: var(--color-primary-dark);
  padding: 2px 10px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
}
.section-label {
  display: inline-block;
  background: #fff7ed;
  color: #b45309;
  padding: 4px 12px;
  border-radius: 6px;
  font-weight: 700;
  font-size: 14px;
  margin: 16px 0 8px;
}
.callout {
  border-left: 3px solid var(--color-accent);
  background: #fffbeb;
  padding: 12px 14px;
  border-radius: 4px;
  margin: 14px 0;
  font-size: 14px;
}
.callout.danger {
  border-color: var(--color-danger);
  background: #fef2f2;
  color: #991b1b;
}
.callout.info {
  border-color: var(--color-info);
  background: #eff6ff;
  color: #1e3a8a;
}

.text-danger { color: var(--color-danger); }
.text-info   { color: var(--color-info); }
.text-bold   { font-weight: 700; }
.underline   { text-decoration: underline; }
.hl-yellow   { background: var(--color-warning-bg); padding: 0 2px; }

/* Image grid */
.img-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  margin: 12px 0 18px;
}
.img-grid.cols-1 { grid-template-columns: 1fr; }
.img-grid figure {
  margin: 0;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 12px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}
.img-grid figcaption {
  font-size: 12px;
  color: var(--color-text-muted);
  font-weight: 600;
}
.img-grid img {
  border-radius: var(--radius-sm);
  background: #fff;
}

.video-wrap {
  position: relative;
  width: 100%;
  padding-top: 56.25%;
  border-radius: var(--radius-md);
  overflow: hidden;
  background: #000;
  margin: 12px 0 20px;
  box-shadow: var(--shadow-sm);
}
.video-wrap iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

.guidelines {
  list-style: none;
  padding: 0;
  margin: 12px 0 0;
}
.guidelines li {
  padding: 10px 14px;
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  margin-bottom: 8px;
  font-size: 14px;
  border-left: 3px solid var(--color-border);
}
.guidelines li strong { display: inline-block; min-width: 22px; color: var(--color-primary-dark); }

/* Footer */
.footer {
  grid-area: footer;
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: 16px 28px;
  text-align: center;
  font-size: 13px;
  color: var(--color-text-muted);
}
.footer strong { color: var(--color-text); }

/* Sidebar overlay (mobile) */
.sidebar-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.45);
  z-index: 40;
}

/* Responsive */
@media (max-width: 900px) {
  .app {
    grid-template-columns: 1fr;
    grid-template-areas:
      "topbar"
      "main"
      "footer";
  }
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    width: 280px;
    transform: translateX(-100%);
    transition: transform .25s ease;
    z-index: 50;
    box-shadow: var(--shadow-md);
  }
  .sidebar.open { transform: translateX(0); }
  .sidebar-backdrop.show { display: block; }
  .menu-toggle { display: inline-flex; }
  .topbar { padding: 0 16px; }
  .topbar-notice { display: none; }
  .main { padding: 20px 14px 36px; }
  .article { padding: 22px 18px; border-radius: var(--radius-md); }
  .article-title { font-size: 19px; }
  .img-grid { grid-template-columns: 1fr; }
}

@media (max-width: 480px) {
  .topbar-title { font-size: 15px; }
  .article { padding: 18px 14px; }
}