cats

Hiya, got two very playful cats that both love to play. However often one ends up watching the other play with X toy. So was wondering if there are any specific toys where cats are "meant" to btoh use it at the same time? If so that would be cool.

So far we've mostly stuck to these original/typical toys, as in, paper bags, mouse on a thread and simple balls with bells, etc.. Feel free to suggest cat toys you've had most success with, need something new for our ones. Anyone here tried these automatically moving balls - any good?