This game is the main game of the interguild, which is a site I started going on in September.
Hannah and the Pirate Caves (HatPC) is an addictive platformer where the goal of each level is to collect all of the treasure chests and then get to the door without dying.
The game has a surprising amount of depth that its user-made levels can achieve. With a variety of different tiles, the user can create several types of traps and puzzles.
User levels can be played by uploading the level code to an account on neopets.com, but you are not allowed to have more than one level uploaded to your account at once. You then enter the name of that account in HATPC's "Load User Level" screen in order to play it. To learn more, and to learn how to make your own user levels, read the Starter's Guide to HATPC
And here are some images to help you understand a bit better: