Games are full of small gaps by design: queues, loads, travel time, cutscenes. Each gap is just long enough for the phone to feel justified and just short enough that you never notice the cost adding up. Across a session it adds up to a lot, and the parts of the game that the gaps connect, the story, the strategy, the actual immersion, are the parts that quietly get skipped.
Telling yourself you will just leave the phone face-down does not survive the first boring loading screen. Reminder apps do not either, because the override is one tap and costs nothing. What works is a limit that refuses to be overridden for free. You set a daily cap on the apps that hijack the lulls, and when you cross it they lock at the operating-system level, not behind a popup you swipe past.
You earn the apps back with something real: 25 camera-counted pushups, 25 squats, 1,000 verified steps, or 10 mindful minutes. Going over never costs money. The only thing you pay is the flat dollar a week, and the overage is settled in reps, which beats sitting hunched for another two hours anyway.