OMG ROBOTSThis is great fun because not only can you invent machines, but you can make little games out of it! (And believe me there are some impressive constructions out there).
As you probably did not know, I am big fan of physics based games and sandboxes. However, this is one of my absolute favorite sandboxes for a few reasons.
- It's physics are more accurate than probably any 2D sandbox I've ever seen, and it has failsafes to prevent people from (easily) breaking the physics engine. (It's waaaay better than Phun/Algodoo in this regard).
- It has cool objects like sliders (for hydraulics and tracks and things) and thrusters and cannons, as well as detailed collision layers and sensors.
- IB2 includes a challenge editor so you can set up specific rules and goals including the option to include an area where users must build a robot to complete a task.
Also I made a short game! I'll post a link to the thread since I already made one. (copy-paste the code into the Incredibots 3 beta):
http://www.incredibots.com/if/viewtopic.php?f=102&t=22782&p=479127#p479127