Circuit Builder is described as 'This App is designed to be an introduction to constructing and operating electronic circuits. Intuitive controls and layout make Circuit Builder the perfect App for understanding the basics of electrical and electronic circuits' and is an app in the Education & Reference category. There are six alternatives to Circuit Builder for a variety of platforms, including Windows, Linux, Mac, Online / Web-based and Android. The best alternative is Circuit Simulator, which is both free and Open Source. Other great apps like Circuit Builder are Circuit Simulator (CircuitJS1) (Free, Open Source), Everycircuit (Freemium), PSIM (Paid) and BrainBox (Free, Open Source).
This electronic circuit simulator is highly interactive giving the feeling of playing with real components. It's very helpful for experimentation and visualization. It's a desktop version of the Circuit Simulator.
Physical things are great. Hardware companies like Apple, Arduino, etc are disrupting our lives in a big way. At BrainBox we love hardware hackers and are in absolute awe of their awesome design and applications they build.