@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

:root {
  --bg: #0a0c10;
  --bg-elevated: #12151b;
  --bg-elevated-2: #171b23;
  --bg-sunken: #0d0f14;
  --border: #22262f;
  --border-subtle: #1b1e26;
  --text: #e4e7ec;
  --text-muted: #8b92a5;
  --text-faint: #5c6377;

  --accent: #5b8def;
  --accent-strong: #7aa2f7;
  --accent-soft: rgba(91, 141, 239, 0.12);
  --accent-border: rgba(91, 141, 239, 0.35);

  --good: #3fb67f;
  --good-soft: rgba(63, 182, 127, 0.12);
  --good-border: rgba(63, 182, 127, 0.3);

  --bad: #e2677d;
  --bad-soft: rgba(226, 103, 125, 0.12);
  --bad-border: rgba(226, 103, 125, 0.3);

  --warn: #d6a94a;
  --warn-soft: rgba(214, 169, 74, 0.12);

  --radius-lg: 12px;
  --radius: 10px;
  --radius-sm: 7px;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.35);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.32);

  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Pretendard", "Apple SD Gothic Neo", "Malgun Gothic", sans-serif;
  --font-mono: "SFMono-Regular", "JetBrains Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 15.5px;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  letter-spacing: -0.006em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--accent-strong);
  text-decoration: none;
  transition: color 0.15s ease;
}
a:hover { color: var(--accent); }

code {
  font-family: var(--font-mono);
  font-size: 0.92em;
}

.site-header {
  background: rgba(18, 21, 27, 0.85);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
  padding: 16px 28px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  position: sticky;
  top: 0;
  z-index: 10;
}

.site-header a.home-link {
  font-weight: 700;
  letter-spacing: -0.015em;
  text-decoration: none;
  color: var(--text);
  font-size: 15px;
}
.site-header a.home-link:hover { color: var(--text); opacity: 0.85; }

.site-main {
  max-width: 980px;
  margin: 0 auto;
  padding: 40px 28px 64px;
}

h1 {
  font-size: 27px;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin: 0 0 10px;
}
h2 {
  font-size: 19px;
  font-weight: 700;
  letter-spacing: -0.012em;
}
.site-main > p {
  color: var(--text-muted);
  font-size: 15px;
  max-width: 680px;
}

.lab-badge {
  display: inline-flex;
  align-items: center;
  padding: 3px 11px;
  border-radius: 999px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 14px;
  border: 1px solid transparent;
}
.lab-badge--before { background: var(--bad-soft); color: var(--bad); border-color: var(--bad-border); }
.lab-badge--after { background: var(--good-soft); color: var(--good); border-color: var(--good-border); }

.lab-instructions {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-left: 2px solid var(--accent);
  padding: 15px 20px;
  border-radius: var(--radius-sm);
  margin: 16px 0 24px;
  font-size: 14px;
  color: var(--text-muted);
}
.lab-instructions strong { color: var(--text); font-weight: 600; }
.lab-instructions code {
  background: var(--bg-sunken);
  border: 1px solid var(--border-subtle);
  border-radius: 4px;
  padding: 1px 6px;
  color: var(--accent-strong);
}

.lab-nav {
  display: flex;
  gap: 6px;
  margin: 20px 0;
  padding: 4px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  width: fit-content;
}
.lab-nav a {
  padding: 7px 16px;
  border-radius: 6px;
  text-decoration: none;
  font-weight: 600;
  font-size: 13.5px;
  color: var(--text-muted);
  transition: background-color 0.15s ease, color 0.15s ease;
}
.lab-nav a.active { background: var(--accent); color: #0a0c10; }
.lab-nav a:not(.active):hover { background: var(--bg-elevated-2); color: var(--text); }

.demo-area {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  margin: 22px 0;
  background: var(--bg-elevated);
}

.lab-source-links {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 12px 18px;
  margin: 0 0 20px;
  font-size: 13px;
  color: var(--text-muted);
}
.lab-source-links a { margin-right: 14px; font-weight: 600; }
.lab-source-links summary { cursor: pointer; color: var(--accent-strong); font-weight: 600; }
.lab-source-links details[open] summary { margin-bottom: 8px; }
.lab-source-links .source-file-list a { display: inline-block; margin: 2px 10px 2px 0; }

.lab-howto {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px 22px;
  margin: 24px 0;
  box-shadow: var(--shadow-sm);
}
.lab-howto h2 {
  margin: 0 0 12px;
  font-size: 13px;
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.lab-howto pre {
  background: var(--bg-sunken);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  overflow-x: auto;
  font-size: 13px;
  line-height: 1.6;
}
.lab-howto pre code { font-family: var(--font-mono); color: #c9d1e3; }
.lab-howto p { margin: 12px 0 0; font-size: 14px; color: var(--text-muted); }

.back-to-list {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 32px;
  padding: 9px 18px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  text-decoration: none;
  font-weight: 600;
  font-size: 13.5px;
  color: var(--text-muted);
  transition: border-color 0.15s ease, color 0.15s ease, background-color 0.15s ease;
}
.back-to-list:hover { border-color: var(--accent-border); color: var(--accent-strong); background: var(--bg-elevated-2); }

.guide-link-banner {
  display: block;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px 20px;
  margin: 20px 0 6px;
  text-decoration: none;
  font-weight: 600;
  font-size: 14.5px;
  color: var(--text);
  transition: border-color 0.15s ease, transform 0.15s ease, box-shadow 0.15s ease;
}
.guide-link-banner:hover { border-color: var(--accent-border); box-shadow: var(--shadow-sm); transform: translateY(-1px); color: var(--text); }
.guide-link-banner small { display: block; font-weight: 400; color: var(--text-muted); margin-top: 4px; font-size: 13px; }

.guide-toc {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 18px 22px;
  margin: 24px 0 32px;
}
.guide-toc h2 { margin: 0 0 12px; font-size: 12px; color: var(--text-faint); text-transform: uppercase; letter-spacing: 0.08em; font-weight: 700; }
.guide-toc ol { margin: 0; padding-left: 18px; columns: 2; column-gap: 28px; }
.guide-toc li { margin-bottom: 6px; font-size: 14px; break-inside: avoid; }
.guide-toc li a { color: var(--text-muted); font-weight: 500; }
.guide-toc li a:hover { color: var(--accent-strong); }

.guide-section {
  margin: 0 0 44px;
  padding-top: 24px;
  border-top: 1px solid var(--border-subtle);
}
.guide-section h2 { font-size: 19px; margin: 0 0 6px; }
.guide-section .guide-lab-link { font-size: 13px; margin: 0 0 16px; display: inline-block; font-weight: 600; }
.guide-section h3 {
  font-size: 11.5px;
  margin: 20px 0 8px;
  color: var(--text-faint);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  font-weight: 700;
}
.guide-section p, .guide-section li { font-size: 14.5px; color: var(--text-muted); }
.guide-section ul { margin: 4px 0; padding-left: 20px; }
.guide-section code {
  background: var(--bg-sunken);
  border: 1px solid var(--border-subtle);
  border-radius: 4px;
  padding: 1px 6px;
  color: var(--accent-strong);
}

.home-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 14px;
  margin-top: 20px;
}
.home-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: var(--shadow-sm);
  transition: border-color 0.15s ease, transform 0.15s ease, box-shadow 0.15s ease;
}
.home-card:hover { border-color: var(--accent-border); transform: translateY(-2px); box-shadow: var(--shadow-md); }
.home-card h3 { margin: 0 0 7px; font-size: 15px; font-weight: 700; letter-spacing: -0.01em; display: flex; align-items: center; }
.home-card p { margin: 0 0 14px; font-size: 13px; color: var(--text-muted); }
.home-card .lab-nav { margin: 0; width: auto; }
.home-card-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 22px; height: 22px;
  border-radius: 6px;
  background: var(--accent-soft);
  color: var(--accent-strong);
  font-size: 11px;
  font-weight: 700;
  margin-right: 9px;
  flex-shrink: 0;
}

.section-label {
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  font-size: 11.5px;
  font-weight: 700;
  margin: 36px 0 2px;
}

.busy-indicator {
  font-weight: 700;
  color: var(--warn);
}