Many players find the game becomes quite difficult by only the third or fourth level, given the number of balls on the field at once.
The trick playing KBounce successfully is to build “corridors”. To build a corridor, start a pair of walls growing close to another wall, and time it so that one of the walls will be hit by a ball and one of the walls will not, and thus become permanent.
This will leave a narrow corridor only a few squares high on the field, surrounded on three sides by walls. Wait for the balls to bounce into the open end of the corridor, and close the corridor behind the ball with a new wall. Although you will most likely lose a life for each corridor created, you can trap several balls in a single corridor.
A final tip — take your time! There is plenty of time, as shown in the Time display at the bottom of the screen. Rushing will just get you in trouble!