Градиентная тень на чистом CSS

by Andrey Dobrovoi

HTML

<button>Поехали !</button>

CSS

@import url('https://fonts.googleapis.com/css?family=Roboto&subset=cyrillic');
html, :root {
  --purple: #7f00ff;
  --pink: #e100ff;
}

body, html {
  width: 100%;
  height: 100%;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-pack: center;
      -ms-flex-pack: center;
          justify-content: center;
  -webkit-box-align: center;
      -ms-flex-align: center;
          align-items: center;
}

button {
  font-family: "Roboto", sans-serif;
  font-size: 16px;
  position: relative;
  outline: none;
  border: none;
  -webkit-appearance: none;
  -webkit-tap-highlight-color: transparent;
  cursor: pointer;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
  padding: 0.75em 1.75em;
  border-radius: 50px;
  display: inline-block;
  color: #fff;
  background: -webkit-gradient(linear, left top, right top, from(var(--purple)), to(var(--pink)));
  background: linear-gradient(to right, var(--purple), var(--pink));
}
button::after {
  content: "";
  position: absolute;
  z-index: -1;
  bottom: -10px;
  left: 5%;
  height: 110%;
  width: 90%;
  opacity: 0.8;
  border-radius: 50px;
  background: inherit;
  -webkit-filter: blur(6px);
  -moz-filter: blur(6px);
  -o-filter: blur(6px);
  -ms-filter: blur(6px);
  filter: blur(6px);
  -webkit-transition: all 0.2s;
  transition: all 0.2s;
}
button:hover::after {
  -webkit-filter: blur(4px);
  -moz-filter: blur(4px);
  -o-filter: blur(4px);
  -ms-filter: blur(4px);
  filter: blur(4px);
  width: 100%;
  bottom: -5px;
  left: 0;
}
button:hover:active::after {
  -webkit-filter: blur(10px);
  -moz-filter: blur(10px);
  -o-filter: blur(10px);
  -ms-filter: blur(10px);
  filter: blur(10px);
}

@supports (-ms-ime-align: auto) {
  button::after, button:hover::after, button:active::after {
    display: none;
  }
}
@media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {
  button {
    background: -webkit-gradient(linear, left top, right top,...