:root {
  --bg: #f9fafb;
  --card: #ffffff;
  --primary: #2563eb;
  --text: #111827;
  --muted: #6b7280;
  --border: #e5e7eb;
  --radius: 10px;
}

* {
  box-sizing: border-box;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
}

/* Layout */
.app {
  display: grid;
  grid-template-columns: 220px 1fr;
  min-height: 100vh;
}

.sidebar {
  background: var(--card);
  border-right: 1px solid var(--border);
  padding: 20px;
}

.main {
  display: flex;
  flex-direction: column;
}

.header {
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 16px 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.content {
  padding: 24px;
}

/* Sidebar */
.logo {
  font-weight: 700;
  margin-bottom: 30px;
}

.nav a {
  display: block;
  padding: 10px 12px;
  color: var(--muted);
  text-decoration: none;
  border-radius: var(--radius);
  margin-bottom: 6px;
}

.nav a.active,
.nav a:hover {
  background: #eef2ff;
  color: var(--primary);
}

/* Cards */
.card {
  background: var(--card);
  border-radius: var(--radius);
  padding: 20px;
  border: 1px solid var(--border);
  margin-bottom: 16px;
}

/* Buttons */
.btn {
  padding: 8px 14px;
  border-radius: var(--radius);
  border: none;
  background: var(--primary);
  color: #fff;
  cursor: pointer;
}

/* Responsive */
@media (max-width: 900px) {
  .app {
    grid-template-columns: 1fr;
  }

  .sidebar {
    display: none;
  }
}