message: Remove `using namespace NAS2D;` from `CheckBox`
diff: #include <algorithm>
  -using namespace NAS2D;
  -
  -
  CheckBox::CheckBox(std::string newText) :
  mFont{fontCache.load(constants::FONT_PRIMARY, constants::FontPrimaryNormal)},
  mSkin{imageCache.load("ui/skin/checkbox.png")}
  {
  text(newText);
  - Utility<EventHandler>::get().mouseButtonDown().connect({this, &CheckBox::onMouseDown});
  + NAS2D::Utility<NAS2D::EventHandler>::get().mouseButtonDown().connect({this, &CheckBox::onMouseDown});
  }
  @@ -44,7 +41,7 @@ CheckBox::CheckBox(std::string newText, ClickSignal::DelegateType clickHandler)
  CheckBox::~CheckBox()
  {
  - Utility<EventHandler>::get().mouseButtonDown().disconnect({this, &CheckBox::onMouseDown});
  + NAS2D::Utility<NAS2D::EventHandler>::get().mouseButtonDown().disconnect({this, &CheckBox::onMouseDown});
  }
  @@ -72,11 +69,11 @@ CheckBox::ClickSignal::Source& CheckBox::click()
  }
  -void CheckBox::onMouseDown(EventHandler::MouseButton button, NAS2D::Point<int> position)
  +void CheckBox::onMouseDown(NAS2D::EventHandler::MouseButton button, NAS2D::Point<int> position)
  {
  if (!enabled() || !visible()) { return; }
  - if (button == EventHandler::MouseButton::Left && mRect.contains(position))
  + if (button == NAS2D::EventHandler::MouseButton::Left && mRect.contains(position))
  {
  mChecked = !mChecked;
  mSignal();
  @@ -109,7 +106,7 @@ void CheckBox::update()
  void CheckBox::draw() const
  {
  - auto& renderer = Utility<Renderer>::get();
  + auto& renderer = NAS2D::Utility<NAS2D::Renderer>::get();
  const auto uncheckedIconRect = NAS2D::Rectangle{0, 0, 13, 13};
  const auto checkedIconRect = NAS2D::Rectangle{13, 0, 13, 13};
  