From the "it might work" department: Wear a hat, or a lanyard, or something else when you're "at work", take it off when you're done. You'll signal to yourself and others the different modes of using the space you're in, and the laptop.

Alternatively, only use that laptop for work, get a different one for non-work, gaming, etc.

You need to get outside for at least 15 minutes twice a day, minimum. No matter how cold, wet, hot, humid, etc.

Set time limits using physical or virtual timers, stop when they tell you to do so.