Creatorverse is a fun free iOS/Android app that is perfect for sparking a kid's creativity. This app focuses on scientific concepts such as: levers, pulleys, joints, and more as a user creates their very own invention and then puts it to motion. This is a very user-friendly app that has users selecting from different shapes, connecting them, adding color, and then watching go into action. Also, a user can browse through other creations and share theirs w/ others.
I highly recommend checking out Creatorverse by clicking here!!!
Below is a brief demo....
Thanks to Edshelf for the tip.