Bought this on a whim for my daughter's 10th birthday. Got some strange looks from the wife but had a fantastic time building it with my little gorgeous princess, She was so excited because she'd "done romans at school" so could relate to it a little. Great to build this but the fun really started when she realised she could fling the plasticine balls with it. We're talking easily 5 metres. Getting the arm with the sling working was a little tricky but the key is setting up the sling in the same position as the picture on the box. We replaced the thin cotton threads with thin string as ensured the 2 ends of the string were tied onto the arm, with thhe third piece of string connected to the washer.
The frame did come apart a few times since we tightened the string a turns or so past the recommended number in the instructions in a bid to get ever greater distance and trajectory but that's a lesson in itself, and using the glue provided it was esily rectified in a few minutes. I would recommend using a few clamps to help the glue set stronger but you can do without although you may be doing a repair job a little more often.
Overall a great "experience" toy and we've had a great time flinging plasticine balls, lego pieces, sweets and teddy bears. Would highly recommend it as a gift to use to share quality time with your kids. Just don't break it when you're playing with it hen they're asleep!