:root {
  --bg: #f5f7fb;
  --panel: #ffffff;
  --line: #cfd7e6;
  --line-strong: #9aa8c2;
  --text: #152033;
  --muted: #5a6780;
  --blue: #2563eb;
  --blue-soft: #eaf1ff;
  --yellow: #f6c343;
  --yellow-soft: #fff7df;
  --shadow: 0 10px 30px rgba(21, 32, 51, 0.08);
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; font-family: Arial, Helvetica, sans-serif; background: var(--bg); color: var(--text); }
a { color: inherit; text-decoration: none; }
code, pre { font-family: Consolas, Monaco, 'Courier New', monospace; }

.app-shell {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 280px 1fr;
}

.sidebar {
  background: #fbfcff;
  border-right: 2px solid var(--line);
  padding: 24px 18px;
  position: sticky;
  top: 0;
  height: 100vh;
}

.brand {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 24px;
}

.brand-mark {
  width: 54px;
  height: 54px;
  border: 2px solid var(--line-strong);
  border-radius: 14px;
  display: grid;
  place-items: center;
  background: repeating-linear-gradient(
    45deg,
    #fff,
    #fff 10px,
    #f1f4fb 10px,
    #f1f4fb 20px
  );
  font-weight: 700;
}

.brand p, .subtitle, .eyebrow, .muted, .card p, .box p, .legend p, .service-card p { color: var(--muted); }
.brand p { margin: 4px 0 0; font-size: 14px; }

.nav { display: grid; gap: 10px; }
.nav a {
  border: 2px solid var(--line);
  border-radius: 12px;
  padding: 12px 14px;
  background: #fff;
  font-weight: 700;
}
.nav a.active, .nav a:hover { border-color: var(--blue); background: var(--blue-soft); }

.sidebar-box {
  margin-top: 20px;
  border: 2px dashed var(--line-strong);
  border-radius: 16px;
  padding: 14px;
  background: #fff;
}
.sidebar-box h3 { margin-top: 0; }

.main { padding: 24px; }
.topbar {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: flex-start;
  margin-bottom: 20px;
}
.eyebrow { margin: 0 0 6px; text-transform: uppercase; letter-spacing: .08em; font-size: 12px; }
.topbar h1 { margin: 0 0 8px; font-size: 32px; }
.subtitle { margin: 0; font-size: 18px; }

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 2px solid var(--text);
  border-radius: 12px;
  padding: 12px 16px;
  font-weight: 700;
  background: var(--text);
  color: #fff;
}
.button.ghost { background: #fff; color: var(--text); }

.page { display: grid; gap: 18px; }
.panel {
  background: var(--panel);
  border: 2px solid var(--line);
  border-radius: 22px;
  box-shadow: var(--shadow);
  padding: 18px;
}

.hero-grid, .grid-2, .grid-3, .grid-4 { display: grid; gap: 16px; }
.hero-grid { grid-template-columns: 1.2fr .8fr; }
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }

.diagram-title {
  font-size: 18px;
  font-weight: 800;
  padding: 10px 14px;
  border: 2px solid var(--line-strong);
  border-radius: 14px;
  background: #fff;
  display: inline-block;
}

.diagram {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 16px;
  align-items: center;
}

.diagram-column {
  border: 2px solid var(--line);
  border-radius: 22px;
  padding: 18px;
  background: linear-gradient(180deg, #fbfdff 0%, #f4f8ff 100%);
}
.diagram-column.right {
  background: linear-gradient(180deg, #fffdf7 0%, #fff8e4 100%);
}

.label {
  display: inline-block;
  padding: 8px 14px;
  border-radius: 999px;
  border: 2px solid var(--line-strong);
  font-weight: 800;
  background: #fff;
}
.label.blue { background: var(--blue-soft); border-color: var(--blue); color: var(--blue); }
.label.yellow { background: var(--yellow-soft); border-color: #d3a119; color: #6b4e00; }

.stack { display: grid; gap: 12px; }
.file-list, .component-list, .service-list { display: grid; gap: 12px; margin-top: 14px; }
.file, .component, .service-card, .mini-box, .level-box {
  border: 2px solid var(--line);
  background: #fff;
  border-radius: 16px;
  padding: 14px;
}
.file strong, .component strong, .service-card strong, .level-box strong { display: block; margin-bottom: 6px; }
.component.example { background: var(--blue-soft); }
.service-card { background: var(--yellow-soft); }
.arrow {
  font-size: 48px;
  line-height: 1;
  color: var(--line-strong);
  text-align: center;
}

.levels {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}
.level-box.code { background: var(--blue-soft); }
.level-box.interface { background: #f9fbff; }
.level-box.services { background: var(--yellow-soft); }

.callout {
  border-left: 5px solid var(--blue);
  padding: 12px 14px;
  background: #f9fbff;
  border-radius: 0 12px 12px 0;
}

.code-block {
  background: #101828;
  color: #eff4ff;
  border-radius: 16px;
  padding: 16px;
  overflow: auto;
  border: 2px solid #2a3650;
  white-space: pre-wrap;
}

.explanation-list { display: grid; gap: 12px; }
.explanation-item {
  border: 2px dashed var(--line-strong);
  border-radius: 16px;
  padding: 14px;
  background: #fff;
}

.footer-note {
  font-size: 14px;
  color: var(--muted);
  text-align: center;
  padding: 8px;
}

@media (max-width: 980px) {
  .app-shell { grid-template-columns: 1fr; }
  .sidebar { position: static; height: auto; border-right: 0; border-bottom: 2px solid var(--line); }
  .topbar, .hero-grid, .diagram, .grid-2, .grid-3, .grid-4, .levels { grid-template-columns: 1fr; }
}