Playfulness in STEM isn't a bad thing.
Pai's Circuit Conductor (69.99) uses a unique mix of Augmented Reality and actual electronic parts that interconnect with magnets to create an electronics learning lab for early school years children.
The set borrows heavily from the playbook LittleBits uses in its STEM kits for older children in that it uses magnetic widgets, each of which has a single function: There are switches, lights, a motor, and even a bit of fiber optics. The pieces snap together with each other or by using magnetic wires. Each "lesson" requires carefully following directions, a skill that it helps develop.
The entire process of building and learning about the way these circuits work is guided by an app. It shows you what to build, and once assembled, demonstrates using an animation how the electricity is flowing. You snap a picture of your completed design and it appears on the screen as a photo and an animated illustration.
Unfortunately, the app is lacking in warmth. One tester said the female voice over reminded her of a teacher she would never want to hang out with. There is a hard balance between imparting information and keeping things entertaining. The best teachers do it every day, but translating it to software has been a longstanding problem in the industry. Most tend to err on the side of "too sweet"; this one is a bit too much like being "in school waiting for the bell to ring". Still, the instructions were informative and explanatory. This, alone, makes it more valuable than kits which really just put boys and girls in the role of factory worker, rather than learner.
As with many STEM toys, this one uses purple packaging to indicate that it is gender neutral. On the other hand the box puts the girl on the back, and features the boy on the cover and six other times on the box.
The entry price of $69.99 seems pretty steep for a set that includes just 12 widgets and some extras. As such it might be better in a classroom. However, the price is in-line with the Little Bits sets, so perhaps that is just the cost of raising a budding electrical engineer. Marked four and up, I think it would be more meaningful for 6 through 8 year olds.