Panel < UIWidget
  phantom: true

ScrollablePanel < UIScrollArea
  phantom: true

FlatPanel < Panel
  image-source: /images/panel_flat.png
  image-border: 1

ScrollableFlatPanel < ScrollablePanel
  image-source: /images/panel_flat.png
  image-border: 1

ParticlesFlatPanel < Panel
  image-source: /images/panel_flat.png
  image-border: 1