body {
  margin: 0;
  background: #0a0f15;
  font-family: 'Segoe UI', Arial, sans-serif;
  color: #e0e0e0;
}

#app {
  max-width: 1200px;
  margin: auto;
  padding: 20px;
}

nav {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
}

.menu-btn {
  background: #111c28;
  color: #6fe3ff;
  border: 1px solid #1d2c3a;
  padding: 12px 18px;
  cursor: pointer;
  border-radius: 6px;
  font-size: 15px;
  transition: 0.25s;
}

.menu-btn:hover {
  background: #173041;
  border-color: #6fe3ff;
  color: white;
}

#sub-menu .submenu-btn {
  background: #0f141a;
  color: #b0b0c0;
  border: 1px solid #222b36;
  padding: 8px 14px;
  cursor: pointer;
  border-radius: 4px;
  transition: 0.25s;
}

#sub-menu .submenu-btn:hover {
  background: #162028;
  border-color: #6fe3ff;
  color: #6fe3ff;
}

#sub-menu .submenu-btn--active {
  background: #162028;
  border-color: #6fe3ff;
  color: #6fe3ff;
}

#content {
  background: #101820;
  padding: 20px;
  border-radius: 8px;
  border: 1px solid #1a2a3a;
  min-height: 400px;
}