DAME is a level editor developed on the Adobe Air platform. Air gives it cross-platform compatibility but seems to require quite a lot of CPU performance. Many of DAME’s features are for editing tile based or isometric maps but it is possible to edit free form layouts as well. This is a Pingus level in DAME using sprite layers:

Pingus level in DAME

Zooming out is disabled by default and enabling it can break map rendering. Air renders everything through the Flash player which seems to eat up quite a bit of rendering performance. It uses custom UI widgets which look and feel slightly different to the platform default widgets.

DAME uses an XML based file format that is easy to read and write, you can attach custom properties to sprites, and you can set a scroll factor on each layer to preview parallax effects. Sprites can be animated and can have per-frame collision data. It is possible to group the sprite information into folders to make it easier to find specific sprites. DAME uses Lua to implement custom level exporters.