Overall, Stones feels like a very successful and strong sound toy prototype! Stones has a very tangible weightiness to the intractable blocks, and they all feel as if they have their own personalities. The combination of materials, and their different acceleration speeds, makes it feel as though the cursor struggles to pick up some of the stones in relation to others. The synth sounds that accompany the movement evokes the feeling of a UFO, as if these blocks are being abducted into space. The round disc of a cursor also lends to that imagery. It was an excellent design choice and instinct to not make the platform cover the entire base of the screen - seeing the surreal loop the blocks make is both satisfying, and there is a lot of fun in tossing them into the void itself. I wonder how this would feel different to use spacial audio instead, and have the noise quiet as it became more distant, and vice versa (though I do think it is nice that it never is entirely silent while off screen). 

If you were to continue working on this, I think it would work in your favor to play into the physicality of the stones. Small changes, such as having them make a sound on impact/landing, and having them cast shadows to see where they will land/where you can place them down would help immensely in making them feel like they 'belong' in this space, and that you are just manipulating their reality. Aesthetically, the cube blocks work very well, and it would be nice to see a continuation of that in a voxel environment for them to be played with in. Perhaps that environment could also potentially be pulled apart piece by piece. Contrasted against a rounded cursor, it would feel all the more otherworldly as your method of interaction.