Android P Developer Preview, and said it will block access to custom overlays. Read: awesome rootless Substratum theming will no longer be possible with P. Bummer.
The irony? The new Android P visuals, heavily leaning to the white and OLED unfriendly variety, have been criticized for being a mixture of Xiaomi's MIUI (the circle switches in the shade) and Samsung's Experience UI (the colorful settings icons), but we need to look no further than some custom Substratum themes available in the Play Store to see where Google got its 9th inspiration from.
Like Flux White, for instance, which, as you can see above, has toggle and settings icons very similar to what Google demos, and on a blindingly white background to boot. To each their own.
source: Google Play