Danger Zone D-21 is the twenty-first level in Danger Zone. The objective of level D-21 is to use the birds to eliminate all the pigs. Get at least 65,000 points for 3 stars.
Send the Red Bird upward so that it just barely gets caught by gravity. If you lucky enough, the upper structure will be collapsed to the downer structure. If not, use Lazer Bird along southern to detonate the TNT on the far side. The corresponding explosion and the already-unbalanced structure should result in a full clear.