reference / interface
slider
A slider in a ui block that gives its number, between a low and a high: size = slider "size" 10 200. It starts at the low end, or at start, and keeps its value as the sketch reloads.
radius_now = 40ui [ radius_now = slider "radius" 10 120 start 40 ]draw [ circle at 200 150 radius radius_now ]
How to write it
slider text low high [start number] [at number number] [width number]
Gives a number.