Here's a well designed 3D pipe puzzle that takes advantage the iPad's slippery screen to serve up 50 puzzles, arranged from easy to hard.

Each puzzle starts with a set of water bears that are sad, dehydrated, and desperately in need of water. The goal in each puzzle is the same, to deliver the colored water to the associated blob-like water bears. You do this by dragging and dropping pipe sections into place.

The pipes come in different shapes and can be rotated with a second tap; or recycled. We would like a more obvious hint system on some of the levels and a better undo, but these are minor gripes -- in all this game is easy to learn and the interface can be used by younger children, despite some reading. Full control over game sounds is given, increasing classroom appeal.

Features of the app include: 50 Puzzles; unlock Challenge Puzzles; and build Pipe Structures in 3D. According to the publisher, "Water Bears was originally designed to give players hands-on experience with Systems Thinking concepts."

In case you're wondering, Water Bears are real microscopic creatures, although they are fictionally presented in this game. There are two editions -- one for consumers, and one for schools via GlassLab. Water Bears EDU is available on the GlassLab platform, where educators can use analytics and classroom management tools, along with lesson plans and other materials to help teach systems thinking. There are no ads or in-app purchases.