How it works
Cooldown keeps one number for your phone: its heat. Time in your hand raises it, rest lowers it, and at 75 the apps you chose lock until the phone has cooled.
Heat
For every 2 minutes in your hand.
For every 6 minutes at rest.
For every 3 minutes resting on the charger.
The scale
Heat runs from 0 to 100. A phone you carry without using it cools like a phone at rest.
What counts as in your hand
Cooldown goes by movement. A still moment shorter than 5 minutes between two handled ones is a phone held still, not a rest. With the screen switch on in Settings, in your hand means the screen is in use: a phone moving in a pocket stops counting as in your hand, and a phone propped up and watched stops counting as resting.
Three levels
Cool
Heat below 40. The eyes are cheerful.
Warm
Heat from 40. The eyes get sleepy. A switch in Settings sends one notification at 40, while a chosen app is in use.
Overheating
Heat from 75. The eyes are on edge, the glass cracks, and the apps you chose lock.
The lock
Which apps lock
You pick them in Apple's own picker: social media, video and games. Phone, Messages, Maps and other everyday tools never lock, even if you pick them. Emergency calls always work.
When it opens
By itself, once the heat is back under 60. A lock never lasts longer than 20 minutes, however hot the phone is. If it ends on that limit with the heat still high, nothing locks again for 30 minutes.
Asking to open a locked app
Write why you need it. In a circle your friends get the question, and whoever answers first decides. If nobody answers in 2 minutes, or you are in no circle, a model decides. Without a connection the phone decides by itself.
What a yes gives
5 minutes of use of the chosen apps within the next hour. A second tap on the locked page, within 2 minutes of the first, gives the same without an answer.
Rest
Any rest counts
Put the phone down and it cools. On the charger it cools twice as fast.
Face-down rest
Lay the phone on its screen. The rest starts by itself and ends when you lift it.
The streak
A day counts for the streak when it has three rests of 30 minutes.
Rest with friends
While a friend's phone rests when yours does, both cool twice as fast. See Circles.