@charset "UTF-8";

/* Root */
* {
  box-sizing: border-box;
}

:root {
  --text-color: hsl(0, 0%, 90%);
}

html {
  color: var(--text-color);
  font-family: sans-serif;
  font-size: 18px;
  background: linear-gradient(90deg, hsl(0, 0%, 10%), hsl(0, 0%, 20%), hsl(0, 0%, 10%));
}

body {
  min-height: 100vh;
  margin: 0;
  display: flex;
  flex-direction: column;
}
header { flex: 0 1 0; }
main   { flex: 1 1 0; }
footer { flex: 0 1 0; }


/* Header */
header {
  width: 100vw;
  border-bottom: 1px dotted var(--text-color);
}

#header-container {
  max-width: 667px;  /* 1080px / 1.618 - Make content area as golden square */
  margin: 0 auto;
  padding: 1rem 1.618rem;
  display: flex;
  flex-wrap: nowrap;
  justify-content: space-between;
  align-items: center;
}

#header-icon {
  flex-shrink: 0;
  width: 3rem;
}

#header-nav {
  display: block;
  padding-left: 0.5rem;
}
.header-nav-item {
  display: inline-block;
  margin: 0 0.1em;
  padding: 0.3em calc(0.3em * 1.618);
  border-radius: 0.5em;
  transition: background-color 0.2s;

  color: inherit;
  text-decoration: none;
}
.header-nav-item:hover:not(.header-nav-item-active) {
  background-color: hsl(240, 0%, 30%);
}
.header-nav-item-active {
  background-color: hsl(240, 50%, 50%);
}


/* Main content */
main {
  margin: 2rem auto;
  padding: 1rem 1.618rem;
  max-width: 667px;
}

h1 {
  font-size: 1.618rem;
  border-left: 15px solid hsl(240, 50%, 50%);
  padding: 0.3em calc(0.3em * 1.618);
  margin: 1em 0;
}

p {
  line-height: 1.5em;
  margin: 1em 0;
}

hr {
  width: 61.8%; /* 100/1.618 */
  border-color: var(--text-color);
}


/* Footer */
footer {
  margin: 0 auto;
  padding: 1rem 1.618rem;
  max-width: 667px;
  text-align: center;
}