Hi Jim,

There are two problems with your script. One is that setting the heading to 180 will not make the ellipse "point back" to where it originally came from - since you are using a random number in the first place you would have to set the heading to the inverse (negative value) of the random number you used to begin with. Secondly, the ellipse will only be redrawn when the script is finished so you won't see the effect of each "forward by" individually but rather the composite effect.

Try something like this instead: Ellipse's x <- 100 + random 10. Ellipse's y <- 100 + random 10. This will make the ellipse jiggle by 10 pixels around 100,100.

Cheers, - Andreas

-----Original Message----- From: owner-squeakland@squeakland.org [mailto:owner-squeakland@squeakland.org] On Behalf Of Jim Ford Sent: Monday, April 21, 2003 3:34 PM To: Squeakland Subject: A seemingly trivial task!

Hi, As a start to a simulation of the transition of states of matter from solid to liquid to gas, I want to make an object (molecule) jiggle about a given x y point. Using tiles, I've tried:

Ellipse heading Random 180 (I would expect Random 180 to return an integer between 1 and 180, but it doesn't

• it returns -180 to +180, but it produces the

right effect!) Ellipse forward 10 Ellipse heading 180 (to point back where it came from) Ellipse forward 10 (to return to the starting x y)

What actually happens is that the object rotates randomly (as wanted) about a fixed point - but the 'Ellipse forward 10' statements don't get executed at all. Is there some preprocessing going on that decides that the net moves are nill, so the Ellipse is not moved at all (like curses iirc)? If so, how do I get round it (using tiles), please? I've tried inserting delay loops at strategic points to attempt to thwart this, also 'Ellipse forward -10' instead of rotating it 180, but the preprocessor's smarter than I am!.

Regards: Jim Ford