Avoide zero delta

Author: monkstone

external_library/java/handy/library/balls/balls.rb

@@ -7,7 +7,8 @@ class Ball
   def initialize(sketch, id)
     @sketch = sketch
     @position = Vec2D.new rand(100..300), rand(100..300)
-    @delta = Vec2D.new rand(-6..6), rand(-6..6)
+    @delta = Vec2D.new rand(0.1..6), rand(0.1..6)
+    @delta *= -1 if rand > 0.5
     @size = rand(60..100)
     radius = @size / 2.0
     @color = BALL_COLORS[id % BALL_COLORS.size]