Tantrix Discovery Puzzle
Start with all the pieces upside-down, then flip over the first three and make a loop the color of the number "3" on the back of the 3rd piece. Then flip over piece number 4 to build a loop in the color of the "4". But make sure all the colored trails match, whether or not they're part of the loop! Use all 10 pieces to make a loop in all 3 colors, one at a time. Think you've got it beat? Add another Tantrix set to make loops using 11, 12, 13 - all the way to 20 pieces! Then add even more sets to continue the challenge! Ages 8-99.
(Don't worry- the example shown above is not an actual solution, so we're not giving anything away!)
I had these in my high school classroom for years and someone would always find them fascinating. I recently re-bought them for the grandchildren. The 3 1/2 year old separates them out by color and makes pathways. The 6 year old can make the simpler closed shapes. The older grandchildren are challenged by the harder shapes. I bought 2 sets so even my adult children have a hard time making an enclosed shape with all 20 pieces.