Busy Shapes (Edoki Academy, 2014; iOS only) is an engaging sorting and problem-solving app based on the work of education expert Jean Piaget.

The app begins with a simple matching exercise: drag a shape to the same-shaped hole and drop it in. These brightly colored shapes represent physical objects such as blocks, sponges, flowers, and buttons. The shapes and holes and appear on a wide range of textured backgrounds, including grass, sand, tile, and wood grain; frequently the next level's background can be glimpsed through the holes in the current level. A correct match is accompanied by a cheery harp-strum sound.

As the app progresses through the 112 very brief levels, it builds upon and combines concepts for increasingly complex reasoning exercises. More shapes and holes in additional colors are introduced for sorting (by shape, size, and color) as are obstacles such as bars or splashes of viscous substances that slow down the movement of your block. In some levels, the shapes move across the screen; in others, you must drop the shape into the wrong hole to move it into a blocked-off area or exchange it for the correct piece.





Shapes and holes are placed underneath objects and must be manipulated into the appropriate slot by a tool. Still other levels require bumping the object into a "transformer" icon to change its color or shape (sometimes multiple times). The shapes themselves become more complex and begin to incorporate secondary colors as well as primary ones.

Success in some of the highest levels seems more luck-based than logic-oriented because the exact objective is unclear. Does a white-outlined hole get a red shape or a blue one? This occasional (and frustrating) lack of clarity may come from the app's wordless format. It may be helpful for caregivers to check out the "grown-ups corner" to read which concept a particular group of levels explores. Also in this adult-locked section are a "walkthrough" (with football play–like diagrams of the correct moves), a "progress report," volume control, and the option to create additional player profiles. Overall, this is an absorbing app for developing critical thinking skills.

Available for iPhone, iPad, and iPod touch (requires iOS 7.0 or later); free this week. Recommended for preschool and primary users.