-Click on the airplane shadow on the right side of the mission selection screen to unlock another level and three new airplanes, including the Raptor and UFO. Note: The airplane shadow does not appear until level 10 is completed.
-In almost all levels are special individual standing palm trees. Shoot those trees down to get 500 skill level points. A message stating "Enemy 's Favorite Tree, +500" will appear. Note: Most levels have more than one of the those special individually standing palm trees.