/* ===== Design tokens ===== */
:root {
  --color-bg: #f7f9fc;
  --color-surface: #ffffff;
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-primary-light: #dbeafe;
  --color-accent: #059669;
  --color-accent-light: #d1fae5;
  --color-text: #1e293b;
  --color-text-muted: #64748b;
  --color-border: #e2e8f0;
  --color-danger: #dc2626;
  --color-warning: #f59e0b;
  --color-node-root: #2563eb;
  --color-node-1: #7c3aed;
  --color-node-2: #059669;
  --color-node-3: #ea580c;
  --color-node-4: #db2777;
  --font-sans: "Pretendard", "Noto Sans KR", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --shadow-sm: 0 1px 3px rgba(15, 23, 42, 0.08);
  --shadow-md: 0 4px 16px rgba(15, 23, 42, 0.1);
  --shadow-lg: 0 8px 32px rgba(15, 23, 42, 0.12);
  --header-height: 64px;
  --a4-landscape-ratio: 297 / 210;
  --max-content-width: 960px;
  --transition: 0.2s ease;
}

/* ===== Reset & base ===== */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  min-height: 100vh;
}

img,
svg {
  display: block;
  max-width: 100%;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover,
a:focus-visible {
  color: var(--color-primary-dark);
  text-decoration: underline;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  top: -100%;
  left: 16px;
  z-index: 9999;
  padding: 12px 20px;
  background: var(--color-primary);
  color: #fff;
  border-radius: var(--radius-sm);
  font-weight: 600;
}

.skip-link:focus {
  top: 16px;
}