The UFO closest to the powder keg storage is killed by standing in a certain spot. Then, the barrels are set up. One extra barrel is placed near the first box to blow up the way inside, then the box on the outside is used to redirect a UFO into it.
Obviously, you can get all 13 bonus coins with this solution. Deluxe W4L4 is now a level that can be solved without a single rainbow coin.
![Wink :wink:](./images/smilies/icon_wink.gif)