On top half of cake, ice sides and top smooth with blue icing. On bottom half of cake, ice sides and top smooth with brown icing. Press brown sugar into brown icing area to resemble sand. Trace lighthouse pattern on cake with toothpick. Pipe-in and build-up lighthouse with tip 10 (smooth with finger dipped in cornstarch). Outline lighthouse, door, windows and railing with tip 3. Cover lighthouse with tip 16 stars. Insert uncooked spaghetti piece into bag filled with black icing and fitted with tip 3, pull out slowly to cover completely. Insert spaghetti piece in top of lighthouse; attach gumball to tip with icing. Pipe tip 7 dot clouds; outline tip 3 trees and birds. Position seashell candies around base of cake.