This game has been a real hit for our 3 & 5 year old. They love watching the marbles go around and the Thunderball is very exciting for them.
The only real learning curve is how you roll the marbles into the arena, as it can greatly influence the result, like if the Thunderball catches any marbles. I've learned if you put the Thunderball on the top it usually catches a few more marbles.
It's mostly a toy at this point but, as the kids get older they will get into the strategy more and more.