This game is a sliver away from greatness.
Please listen devs!
The ball rolling sounds are fantastic and relaxing. The puzzle completion sounds are jarring and, arguably, grating.
Please add a volume slider for all sound effects outside of ball rolling sound and a dedicated slider *just* for ball rolling sounds.
To me, this would amplify this games potential for relaxing play, immeasurably.
Also, a nice feature set to consider for next time are compatible goals. For example either 3 gems or 1 ball or whatever. Sort of an accomplishment checklist effect. Adds an addictive element, like how you can play a course in Super Stickman golf, just for par, do it "clean ball" and then do it 10 under par. You dont have to do all at once. Adds accessibility and replayability. Your current goals are more perfection oriented but that adds a "wall effect" for less dedicated users and can be covered by an "aced it" check box. Just a thought.
Edit: wull add a much deserved praise for the GORGEOUS artwork.
Visiblemode about Slingshot Puzzle, v2.0