Spiralgraph. Spent hours working on these as a kid. Got an original one that was barely used off of ebay and gave it to my kids when they were both 8 yrs old in 2009. They spent about 30 minutes seeing what they could make, then bored. I sat down and created a few beautiful designs. Love my kids but thankful I was a '70's kid who thrived on being creative and inspired by what I could do with simple tools and not a video game remote.