The directions are kinda hard to follow. If you are buying this for a child then strongly recommend that you help them put it together. The wire Leads are also very delicately soldered onto their contact points. I had to resolder a couple of them that broke during assembly. Works great outside though!That’s good enoughanother broken toy as soon as I put it together it broke... ANOTHER SAD CHILDThe concept is great but we were surprised at how complicated the instructions looked. We haven’t gotten around to putting it together because they didn’t look very user-friendly.I like that me and my daughter got to bond and build something together. Well written instructions and was exactly as discribed and has multi-functions to adjust almost everything battery or sun it will surprise you how well the gears work. Gave my daughter a since of accomplishment great product.Bad assembly instructions. Solar panel does not work.This item came quick. I bought it for a 6 year old boys birthday. He was extremely excited. He loves science and building so this stem car was a perfect gift. He did need help building it but it worked great. I would buy it again.I am a grown man and I have built very complicated machines and electronic devices, so we can rule out user error. I see a lot of reviews here are from grandparents who bought these for their grandkids. What I don't see are the experiences of the disappointed grandkids and anguished screams of their poor tortured parents. The instructions are badly translated, the pieces are not clearly marked, the assembly diagrams are meant for those with advanced degrees in mechanical engineering, the brittle wires snap from their soldered terminations. But the biggest injury inflicted by this kit is that once assembled it just barely moves. My kids looked at it and told me to make it go faster. Yeah, I'm sorry children, we've been screwed. I bought two and after the first one, I'm sending them back.