As mentioned above, on order to have enough energy for playing, a cat must get plenty of sleep. It is generally not difficult to find a comfortable place to curl up. Any place a human likes to sit is good, especially if it contrasts with your fur color. If it s in a sunbeam or near a heating duct or radiator, so much the better. Good places also exist outdoors, but you have the disadvantages of being seasonal and dependent on current and previous weather conditions such as rain.
Open windows are a good compromise.
They are very protective of what they think is their property and will object strongly if they catch you sharpening your claws on it. Being sneaky and doing it when they are not around won t help as they are very observant. If you are an outdoor kitty, trees are good. Sharpening your claws on a human is a definite no-no. It is important to maintain one s dignity when around humans so they will not forget who is the master of the house.