You've solved it by now, I'm sure, but my advice would have been to only process touches on the composite sprite, not on each limb.

Also, you can of course create your 3x texture at, say, 2048x2048 px. Then everything is clearly mipmappable on a 3x device, but not on a 2x or 1x device. My assumption here is that you'll want all textures to have the same point size, to keep the measurements in SpriteKit the same.

You apparently have to override your components' supportsSecureCoding property to return true, in order for them to be serialized or deserialized correctly.https://stackoverflow.com/questions/58698088/does-xcode-11-2-scene-editor-allow-adding-components

You could use touchesBegan, –Ended, –Cancelled, and –Moved instead of a gesture recognizer.

Traditionally, game developers have used an in-game console.

Change the gravity in physicsWorld.

There are only 32 bits in the bitmask. These bits are for allowing types of contact, or contact between types of nodes. You should use just one of the bits for all these balls. The contact test delegate will get called for each pair of nodes. In the contact test delegate, examine the ball node and make the changes you need.

What's wrong with the code you've commented out? Though I think the type ought to be Task.Handle<…>.

Presumably you'd use UIViewRepresentable to wrap the SKView. The code to deal with the nodes would depend on the details of your application.