[Squeakland] feature request: rotation center help

Alan Kay alan.kay at squeakland.org
Fri Feb 17 08:36:54 PST 2006

For older children, you should do real inverse square orbits. Squeak Etoys 
does these very well. Don't forget that you can choose to have the "origin 
at center" in any playfield. This means that any player put in a playfield 
will also act as a vector, and this can make it very easy to model 2D 
accelleration, velocity and position. (There is also a vector vocabulary 
for players which can be turned on to allow simple + and - vector 
arithmetic to be done between players, etc.)

A fun thing to do (especially since it is intractable with classical math) 
is to do the 3 to n body calculations. Turn the pen on for the third body 
and you get beautiful chaotic curves, etc.

Also, when using embedding, think about what it means for each player to be 
a coordinate system for the players embedded in it.



At 04:34 PM 2/16/2006, Randy Heiland wrote:
>Might it be possible someday to add a line to the balloon help for a
>sketch's rotation center to "press Shift to move" -- assuming this action is
>required across operating systems.  Not having this causes some frustration
>in workshops.
>Squeakland mailing list
>Squeakland at squeakland.org

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