http://advsys.net/ken/download.htm
You type in some C-ish code, it gets immediately executed and drawn. Instant feedback was a winner feature here. Graphing y=f(x) was AFAIR as simple as typing "(x)" in the first line and writing an expression in the next. "(x,t)" for time-varying singals, "(x,y)" for 2-d functions with values viewed as colors, "(x,y,z,&r,&g,&b)" for full-voxels, etc.
I don't even remember how this little program found its way to my hard drive, but I had a lot of good times with it.
Me and my boyfriend are both math nerds and will both love this :)
It was as game-like as most entertainment software of its time, but it subtly forced me to learn some math in order to create complex shapes.
I think of Minecraft as a similarly clever idea.
The physicality of the Logo turtle robot we had at our school back in the eighties was what made it "click" for me. Playing with something connected to the real world takes it to another level.
http://el.media.mit.edu/logo-foundation/what_is_logo/history...
But Scratch is one step up the ladder to me. It is a commitment to an eco-system and a super nice but blank canvas.
I find Logo to be simpler and more limited. This is a "good thing"(tm) when getting kids hooked. The first hit should always be free :-)
I have gotten some of my non-technical friends to buy mbots. They like the idea but the learning curve was to steep for them.
Their hardest struggle was dragging the blocks around with the touchpad. It would have been less frustrating to have a keyboard-based interface I think. (Now that I type this, I realize maybe I should have tried a two button mouse for them.)