React all balls by make them collide to a same level reacted (or reacting) ball. A reacted ball can increase its level by one by causing one reaction on other balls (white or same level one). Two modes available to play:

Fate : Balls bounce on wall hit. No more attempt needed.
Skill : Balls cross over wall. Click small balls to change their direction randomly.

Bubo 4K is entry for Java4K 2012 session, finished 46/51 on both community votes and judging results with overall 69%.