Today's app is going to blow your mind. Back in 1986, artist Mike Wilks published a book called The Ultimate Alphabet, which featured 26 different paintings, each filled with items that corresponded to the letters of the alphabet; the letter A painting contains airplanes, ants, an apple tree, and so on. There are more than 7,777 words represented in the book, with lots more little secrets hidden in the paintings; there are letters encoded in Morse code or semaphore, obscure symbolism, and visual gags.
The book was part of a competition with a big cash prize, which was solved in 1988, when Wilks published The Annotated Ultimate Alphabet; it included descriptions and clues for each of the items hidden in the extremely detailed paintings. Now, a company named Toytek has begun to bring the book to the iPad, and it allows you to interactively explore some of Wilks' paintings and their extremely deep complexity.
As you can see above, it's wild; you tap on an item, enter the actual name, and then the book will tell you whether it's right or provide clues for the word you're looking for. The app is free to try, though it's prohibitively expensive if you want to purchase everything. You can buy the letters in bundles, and the full purchase price eventually comes out to around US $45 in total. That's pricey, although it's the same cost as the printed book, and you get the interactivity for free. Still, it's a great idea, and there is a free trial if you want to check it out.
Update: We're told that due to user input, the free version has been changed from a timed trial to simply having the entire letter A be completely free to play all the way through. Enjoy!