[saver] Add balls to the field

MetaballsSaver/MetaballsSaverView.swift

@@ -63,6 +63,11 @@ public class MetaballsSaverView: ScreenSaverView, RendererDelegate {
             ])
             renderer.delegate = self
         }
+
+        for _ in 1...10 {
+            addBallWithRandomRadius()
+        }
+
         super.startAnimation()
     }
 
@@ -80,6 +85,15 @@ public class MetaballsSaverView: ScreenSaverView, RendererDelegate {
         return window
     }
 
+    // MARK: - Private
+
+    private func addBallWithRandomRadius() {
+        let base = UInt32(bounds.width * 0.05)
+        let variance = UInt32(base * 2)
+        let r = Float(base + arc4random_uniform(variance))
+        field.add(ballWithRadius: r)
+    }
+
     // MARK: - RendererDelegate
 
     public var renderSize: Size {