Tapping its expertise in digital learning experiences for preschoolers, PBS KIDS has released WordWorld Tales, the US pubcaster’s first appisodes app based on one of its TV properties.

Now available as a free app for iPhones and iPads, and targeting three to five-year-olds, WordWorld Tales teaches early literacy skills and currently features four exclusive touchable appisodes (two for free and two for purchase).

On the free side, Happy Birthday, Dog! lets users collect birthday supplies for main character Dog’s surprise party while introducing and fostering print awareness, letter recognition and word building.

A Christmas Present for Dog, the app’s additional free appisode, follows a saving Christmas storyline and focuses on writing letters, letter recognition and word building.

Parents can pay to access Pirate Ship: Sheep, Duck and Shark and Superhero Sheep. Two new additional appisodes are expected to launch soon.

The app release comes on the heels of extensive multiplatform growth for PBS KIDS, which recently unveiled its new branded YouTube channel, a second app based on its hit PEG + CAT animated television series and robust web and mobile plans for its upcoming series Nature Cat.