What's the substitute for ::shadow and /deep/?

Question

The two shadow-piercing combinators have been deprecated as stated in https://www.chromestatus.com/features/6750456638341120
Then what\'s the substitude for achieving the

Answer 1

As of Polymer 2:

• ::shadow (shadow-piercing selectors) - there is no direct substitute. Instead a custom CSS properties has to be used. Polymer 2: Custom CSS Properties

• /deep/ - there is some sort of replacement by defining :host > * { ... } (applies a ruleset to all of the top-level children in the host's shadow tree, which doesn't conflict with the rule in the main document).

For more detailed information check Polymer 2 Upgrade Notes