So I have kids and I am constantly looking for fun, educational, entertaining, games for them to play.  I like discovering open source free applications that satisfy this most of all.

Some examples of great programs: tux paint and tux typing.

Phun is different.  Where those two programs excel in teaching kids, Phun is just fun.

It's interactive in a way that not many programs are.  It actually has the playability that feels much like an RTS.  It does what you make it do now.  You add something and the environment acts upon it.

Watch this video.

And it's a toy...except it isn't: 

Radial engine:

Gears:

It's a remarkable achievement.

One big benefit I see in Phun over the other kid applications I've found is that Phun uses an almost standard application user interface.  The user needs to navigate menus and toolbars and context menus.  The other kid apps focus on learning something or doing something.  Phun does that also, but because of its complexity the standard UI is leveraged as the simplest solution.

This is a great side benefit.  Kids get exposure to the standard UI and how applications work.  This has direct impact on any and all other applications they might encounter.

If you have kids go get this program now.  Install it, run it and watch your kids be sucked in for hours.  Heck go do it yourself.  It's really addicting.