CSS горизонтальный линейный градиент
background: linear-gradient(to left, red, blue);
Friendly Hawk
background: linear-gradient(to left, red, blue);.foo {
background-image: linear-gradient(red, blue);
}background: linear-gradient(to left, #333, #333 50%, #eee 100%);/*From bottom to top*/
background: rgb(166,166,166);
background: linear-gradient(0deg, rgba(166,166,166,1) 0%, rgba(255,255,255,1) 29%);Gradient Generator:
https://freetoolssite.com/tools/gradient-creator-onlinebackground: linear-gradient(Direction (keyword or degrees), color1 10% (10% width), color2 width (it's not neccessary), ...);