The build is not hard, and the instructions are clear enough, but you have to be very careful (as with all vex builds) to do it EXACTLY right or you'll have trouble or it won't work. The instructions that came with my set were clearly printed except for the one page that had some key gear positions (figures) which would have made the build impossible except for the online instructions (same as printed, but clearer). Saved the day. Build went smooth and fast after that. Orbit works great, no stiffness or other issues with gearing. Only compliant is the pegs meant to hold the "sun" don't fit in the hole and the Sun falls out. Easily fixed with another vex part we had laying around. Not sure if this is a design flaw, but seemed like it. Bottom line is my 8 year old son loves it and uses it daily. One crank = one day. This thing is fun and shows science in action. I haven't been happy with other vex hexbug products (quality was poor), but this one is fun and works well.
Review by budding_Gallieo (Posted on 7/17/2016)
The Hexbug comany should definitely redesign this model before selling any more of them.
The set wasn't too hard to put together, but when I tried to turn the wheel to move the Earth, it was so stiff that it couldn't be done. After further examination I discovered that it was caused by a gear sandwiched too tightly between two other pieces. If you try and remove the pins holding the two pieces together, the top portion of the model will fall off. I read several other reviews of this product with the same complaint.