New button style for Untropy Start Page

http://untropy.net/start/

by Andrew Holloway

HTML

<main>
<button>
<span>Test</span>
</button>
</main>

CSS

:root {
  --button-radius: 5.5rem;
  --button-color-inactive: #0070D3;
  --button-color-active: #005aab;
  --button-color-focus: #0086FF;
  --button-text-inactive: #eee;
  --button-text-active: #ddd;
}

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
}

main {
  width: 100%;
  height: 100%;
  
  /* top-left corner */
  background-image: linear-gradient(135deg, #acf, #3366a0);
  
  display: flex;
  justify-content: center;
}

button {
  align-self: center;
  padding: 1rem 5rem;
  
  border-radius: var(--button-radius);
  border: none;
  
  background-color: var(--button-color-inactive);
  color: var(--button-text-inactive);
  
  font-family: apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Oxygen,Ubuntu,Cantarell,"Fira Sans","Droid Sans","Helvetica Neue",Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";
  font-size: 1rem;
  letter-spacing: 0.1rem;
  
  box-shadow: -5px -5px 5px rgba(255, 255, 255, 0.2), -1px -1px 0 rgba(255, 255, 255, 0.3), 1px 1px 0px rgba(0, 0, 0, 0.15), 5px 5px 5px rgba(0, 0, 0, 0.5);
  background-image: linear-gradient(135deg, #00000000, #00000090);
  
  transition: box-shadow ease-in-out 1350ms;
}

button:active {
  background-color: var(--button-color-active);
  color: var(--button-text-active);
  
  box-shadow: 1px 1px 1px rgba(255, 255, 255, 0.5), inset 1px 1px 1px rgba(1, 1, 1, 0.5);
}

button:active span {
  font-size: 0.95rem;
}

/* a11y */
button:focus {
  border: 0.25rem solid var(--button-color-focus);
  outline: none;
}