The open source version of World of Goo
Building bridges in OpenGOO
You may remember that in the first Humble Indie Bundle, World of Goo was not open-sourced. Well, there is an active open source clone called OpenGOO being developed. It uses OpenGL, Box2D and is GPLv3-licensed.
Basic layers of level creation in OpenGOO
A Shotgun Debugger level viewed in Inkscape
There are instructions available for creating levels. Inkscape is used for that purpose, just like in Shotgun Debugger! A method I would love to see being widely used in games that allow for user-generated content in general.
SuperTuxKart level editor (hint: it’s Blender!)
Speaking of not-re-inventing-wheels: the team behind SuperTuxKart recently posted an article about using Blender as a level editor, rather than writing and maintaining an own content creation tool, which I highly recommend to all developers of 3D games with ‘traditional’ engines.