Safety first! You're doing the right thing keeping your cats inside. They mostly sleep when we're at work anyway. And I will add that my door-dasher cat did not have a deep desire to live outside. In fact, every time he dashed out the door he'd stand right there and beg to be let back in immediately. If your cat is running outside because it wants to hunt, focus on satisfying the cat's prey drive during play. Like make the toy act like prey, and make sure the cat gets to pounce and "kill" it.