[qplex]

Using a smartphone or a tablet computer for 2 hours straight will result in a negative physical condition so it is no wonder if the kids are cranky after that.

Also disrupting "flow" can make people cranky since its hard to attain that kind of a mindstate (a lot of work can go to waste if somebody interrupts you).

Anyway... I've seen kids playing Pokemon Go running around the neighborhood and the forests near by, and they seem like happy campers. It's good that there is at least something that makes kids play outside these days.