Inkredibles: Word Power for Curious Kids Invisible Ink Activity Book is packed full of fun superhero-themed language activities, including crosswords, problem solving, acrostic puzzles, word searches and more! Word fiends can match wits with the word puzzles featured in this incredible Invisible Ink book. Use the Invisible Ink pen to answer the questions and unmask the hidden answers within. Each language-focused activity features a superhero theme, which makes learning a ton of fun!