As you lie in bed, snug under the covers, your kitten stalks your right leg, quietly, stealthily, like a ninja. You make the faintest move – no more than a quiver really – and in a split second she leaps onto your calf. How can your kitten be so adorable and such a holy terror at the same time? If she’s between 3 and 6 months old, such intense play is normal: It is up to you to properly hone and direct her seemingly boundless energy. When properly fed and in good health, kittens between 3 weeks of age and one year old have an intense urge to play. Their lives at this stage revolve around playing..