Merry Christmas by Inorder Traversal

Description

A dark, starry background contains a binary tree made of colored circular nodes connected by thin gray lines. The node labels are letters: the root is "R"; its left side contains "R", "E", "C", "M", "R", "Y", and "H"; its right side contains "M", "S", "A", "I", "T", and "S". Read with an inorder traversal, the labels spell "MERRY CHRISTMAS," turning a holiday greeting into a data-structure exercise.