:root {
  --custom-accent-color: rgb(195 239 173);
  --custom-darker-color: rgb(66 104 51);
  --custom-bg-linear: linear-gradient(to bottom, #52c234, #061700);
  --custom-bg-webkit-linear: -webkit-linear-gradient(to bottom, #52c234, #061700);
  /* find color pair from https://uigradients.com/ */
}
html{
  height: 100%;
}
body {
  background: #fff url(../img/dominik-schroder-FIKD9t5_5zQ-unsplash.jpg) no-repeat center bottom fixed;
  background-size: cover;
  /* background: #2980B9;  */ /* fallback for old browsers */
  /* background: -webkit-linear-gradient(to top, #FFFFFF, #6DD5FA, #2980B9);  Chrome 10-25, Safari 5.1-6 */
  /* background: linear-gradient(to top, #FFFFFF, #6DD5FA, #2980B9); W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+ */
  }
.welcome-header img {
  width: 72px;
  margin-bottom: 40px;
}
.container {
  margin: 4em 2em;
}
.tree {
  margin: 0 auto;
  text-align: center;
  width: 100%;
  max-width: 800px;
}
.tree .header {
  text-transform: uppercase;
  font-weight: 600;
  margin: 2em;
}
.tree .links a {
  margin: 0.75em auto;
  min-width: 20em;
}
.tree .footer {
  margin: 2rem;
}
.header .logo {
  width: 128px;
  margin-bottom: 8px;
}
.header .bi {
  color: var(--custom-darker-color);
}