Endless Reader

Endless Alphabet has developed a sequel that is (if possible) even better than the first.  Or at least an excellent successor.  Endless Reader incorporates both spelling simple words (letter-by-letter) and then building sight-word skills by reconstructing a sentence that the wacky monsters have scattered.  Players are then rewarded with humorous animations that illustrate the sentence.  The app itself (with some words) is free, and you can purchase more "word packs" as your child progresses.  Very highly recommended.