World 2 - Level 4
Cannons, Chompers, Kaboom!s, Oh My!
First move the two boxes along the blue path to trap and explode the Kaboom! at the blue cross. Use eight steel boxes to build two bridges across the lava as indicated by white arrows. Push the final box along the upper brdige to get it onto the yellow button. Collect coins.
Now move (quickly) to the purple "x" at the edge of the level. Wait there until Chomper follows you onto the purple button. Now move left and have Chomper follow you onto the green button. This will activate the cannons, which will pick off chompers and boxes, allowing you to exit the level through the red teleporter.