[chrishtr]

The <dialog> element is fully styleable, including its backdrop (the MDN article explains how for the latter). In Chrome you can also fully style animations opening and closing a <dialog> or popover.

https://developer.chrome.com/blog/entry-exit-animations

[salzig]

@starting-style support is quite good in all browsers, not just chrome. https://caniuse.com/?search=%20%40starting-style