Added a low level constraint mechanism as suggested by @LeaVerou It's intentionally low level (just a function you need to implement to constrain a thumb) so you can create any sorta constraint. Here's one where you restrict thumb to within a circle: https://glitch.com/~planar-range-disc https://twitter.com/preetster/status/1252313386349506560

Or restrict to just a ring: https://glitch.com/~planar-range-circle

Or a triangle: https://glitch.com/~planar-range-triangle

And finally, you can create different restrictions for different thumbs. Combining it all: https://glitch.com/~planar-range-triangle-colors

I can imagine simpler higher order custom elements with this as the base to just draw circles or just do triangles, also convert the coordinated appropriately to radial values.

Something like <circular-range r="10" angle="45">