smallest first ➜
Star!
Penny the pelican runs the post office and the mail is all jumbled. Every letter has a big house number, and the mail must go out smallest number first. Do it in three steps. One: tap a letter, then tap the bag it belongs in. Each bag is a group of numbers, like 20-29. Two: Penny opens one bag at a time and you tap the smallest letter in it, again and again, until the bag is in order. Three: watch the mail truck drive down the street and drop every letter at its house.
Stuck? Tap Help me and the right letter or bag glows. Finish with no wrong bags and no wrong picks for a star. When the truck is done Penny shows you the trick you used, called Bucket Sort: put things into small bags first, sort each small bag, then join the bags in order. Every delivery wins a stamp for your collection.