Thanks for the level Deetster, and thanks for the hint Amnon. I had problems to get the timing right, but finally I got the idea to count how many times the chomper opens and shuts its mouth each time the cannons shoot, and all I had to do was pushing the box at 15
Good strategy Marinus. Yeah, generally you had to find a method like that to get the timing perfect, because waiting for it to actually happening didn't work out to be quick enough for me at least.