A reflection flashes across the floor and your dog pounces. Soon they are scanning the room for the next flicker, even after the light is gone. That is when the game stops looking like play. Repetitive light or shadow chasing can become disruptive and hard for a dog to leave behind.
Don't make the pattern stronger with a laser pointer or by reflecting light for entertainment. Reduce predictable flashes from phones, mirrors, or watches where practical. If your dog chases light often, cannot settle afterward, seems distressed, or the behavior began suddenly, make a veterinary appointment. Pain, neurological, and other medical problems may need to be ruled out before treating it as behavior alone.
Notice the pattern without testing it
Write down when it starts and how long it lasts. Does sunlight cross one wall at a certain hour? Does it happen after a frustrating event or when your dog has been pacing? A brief video may help the veterinarian, but don't create flashes to get footage. If your dog can still engage in another activity before the chase begins, invite them to sniffing or a food puzzle at a calmer time. Do not repeatedly call them away only to expose them to the same flashing light.
A qualified veterinary behavior professional may be needed when the behavior interferes with rest or ordinary activities. More exercise alone is not a diagnosis or a cure. The useful first move is to stop producing the trigger and ask what is driving the repetition.
Sources: VCA Animal Hospitals: Compulsive Disorders in Dogs. Prosper Animal Hospital: Laser Pointer Syndrome.