Dogs with limited mobility for any reason, including age, can still enjoy a good game as long as it takes their abilities into account, rather than any disabilities. If short walks (or no walks at all) are all your dog can manage, they still have a brain that needs to be kept active. Dogs will always have their sense of smell, so hide some treats (or a portion of their dinner) among some scrunched up old newspapers in a cardboard box and let them have a good rummage around. A shallow box works well for dogs who may want to play when lying down, for smaller dogs, get a big box and cut a hole so they can get right in. Hiding food in your dog's blanket can do just as well, but use dry biscuits so they don't go mouldy if they aren't found. Float a treat or a toy that your dog loves in a bowl of water and let him work out how to fish it out - then let one sink and have him learn to dip their nose in. You can also create tasty ice-cubes by putting a small piece of hot dog sausage, tuna, or anything else your dog likes into ice-cube trays, covering with water and freezing. These can then be scattered around the garden, left in a bowl, or again, dropped into water so your dog can learn to dip his nose in to fetch them.