Click and drag in the canvas window. The faster you drag, the bigger the circles are. Best viewed in Chrome or Safari.
1) (20%) Enable the checkbox - checking it will cause all of the circles to be drawn at 50% alpha.
2) (30%) Create an additional variation of this speed circle theme, or on a similar theme such as symmetry. This should be SIGNIFICANTLY different from the base files. Tell us what the variation is so that we can read it right here: Symmetry theme with both x/y and reversed y/x
3) (20%) Circle traits are based on mouse position or movement speed. Brush size *= x / (y + x)
4) (30%) Slider affects circle drawing. The slider should show an obvious visual effect to the circles.
Check out the Khan Academy examples (written in processing) here: Speed Circles & Symmetry
Here's our original Speed Circles JS, and in-class variation example: Speed Circles JS 2.