By mid-October, the light starts leaving early. The birds that crowded the feeder in August have thinned out, the squirrels are busy somewhere else, and by the time you're home from work, the window your cat spent all summer staring through is mostly a dark rectangle. The days feel shorter to you. To an indoor cat, the whole show just got canceled.
Figuring out how to keep an indoor cat entertained through the darker months doesn't take a room full of gear. It helps to think about what your cat is built to do, which is hunt, and about the senses it uses to do it. Give each of them something to work on, and the season gets a lot more interesting from where your cat sits.
For the eyes
A window is the easiest thing you can offer, and it matters more than it might seem. Ohio State's Indoor Pet Initiative compares the view outside to television for a cat: leaves dropping, birds coming and going, insects, the odd squirrel darting across the yard. As the seasons shift, so does the programming, and as fall slides toward winter, there's less of it to go around.
You can improve the reception. If your cat has only one good window, give it a second. A spot by another window lets it switch channels when one view gets dull. It doesn't have to be anything built for cats, either. A chair or a small table pulled up to the glass works, as long as your cat can settle there and see out. And if you have a yard, a bird feeder within view of the window gives the birds a reason to keep showing up.
On the darkest afternoons, bring the view indoors. A nature video with birds or small animals on the move can hold a cat's attention, and a fish tank gives it something live to watch. Neither replaces you, but both are good for the stretches when you can't be there.

For the ears
A cat's ears are part of the hunt, too. Toys that squeak, chirp, jitter, or swing come across like something alive, and that's often what gets a cat off the sofa in the first place. A furry mouse that makes a small noise as you roll it past can do more than a silent one that just lies there.
Sound works best paired with movement. A crinkly toy dragged slowly along the floor, disappearing behind a chair leg and reappearing, is far more convincing than one shaken in the air. Keep the noise small and quick, the way prey would be, rather than loud and constant.

For the paws
This is where most of the fun happens, and where your part matters most. Set aside a regular time for play every day, so it becomes something your cat can count on. Many cats seem calmer through the rest of the day when they know a session is coming.
Start by figuring out what your cat likes to catch. Some cats go for anything that flies, like feathers on a wand swooping overhead. Some prefer things that scurry along the ground, like a furry toy or a ball. Others want tiny, fast, twitchy things, like a knotted string or a treat skittering across the floor. Try each kind for a minute and watch which one gets the tail twitching, then shop for more of that.
A few ideas that cost almost nothing: drag a shoelace around the house and up onto the furniture your cat is allowed on. Hide a toy under a blanket and wiggle it so your cat has to dig. Set a paper bag on its side on the floor, and once your cat is inside, scratch the outside with a fingertip.
That fingertip is as close as your hands should get. Hands and fingers aren't toys. A cat that learns to pounce on them will keep doing it, well past the point where it's cute. Keep a wand or a string between you, and if play gets too rough, stop and pick it up again once your cat has settled.
Finally, don't leave every toy out all the time. Keep a few around during the day and save the favorites for your play sessions, trading them in and out every so often. A toy that disappears for a week comes back feeling new.
A side table at the window end of the sofa can hold the wand and favorite toys between sessions and still look like living-room furniture.

For the appetite
Every hunt ends with a meal, and you can borrow that too. Toss a piece of dry food or a treat across a smooth floor and let your cat run it down. Or fill a ball with a few bits of food, so batting it around eventually pays off. From your cat's point of view, it's earning dinner the old-fashioned way.
Food toys are also one of the better answers if you're wondering how to keep an indoor cat entertained while you're at work. Toys your cat can bat, pick up, and toss on its own help fill the hours when nobody's around to hold the wand, and a treat-filled one gives it a reason to keep at it.

When the light goes early
The days will keep getting shorter for a while yet. None of this needs to fill your whole evening. A good window, a toy that sounds alive, ten minutes with a wand after dinner, and a few treats that have to be chased down will cover a lot of ground. It also helps to have one calm corner that stays set up, a place where the toys have a home and your cat has a spot of its own. Your cat still has plenty to see, hear, catch, and eat. It just needs you to set it up.
If you're setting up a play corner at the end of the sofa, here's a closer look at the Nest Side.