Blizzard is in full damage control mode after the internet assumed it was shutting down development on a World of Starcraft mod that violated their trademark, despite using their own in-game tool set.
It's designed to tell when you're actually looking at your screen, keeping its sleep mode from kicking in when you are and shutting down to save battery life when you're not.
Xperia ZL also includes Battery STAMINA Mode that significantly improves the battery standby time by automatically shutting down battery-draining apps whenever the screen is off and starting them up again when the screen is back on.