:root {
  --font-size: 18px;
  --color-text: #222;
  --color-background: #fff;
  --color-accent: #fddd34;
  --color-background-footer: #222222;
  --color-footer: #f6f7f9;
}
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
html,
body {
  min-height: 100%;
}
body {
  display: flex;
  flex-direction: column;
  font-family: Open Sans, Roboto, system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI',
    Oxygen, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;
  color: var(--color-text);
  background-color: var(--color-background);
}
header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  padding: 0 80px;
}
header h1 {
  font-weight: 900;
  font-family: Roboto, system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI',
    Oxygen, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;
  font-size: calc(var(--font-size)*2);
  margin: calc(var(--font-size)*3) 0;
  margin-right: auto;
}
img { max-width: 80%; }
a {
  color: #222;
}
h1 a { text-decoration: none; }
button,
.btn {
  cursor: pointer;
  text-decoration: none;
  line-height: calc(var(--font-size)*2.56);
  color: var(--color-text);
  border: 2px solid var(--color-text);
  text-align: center;
  font-size: var(--font-size);
  display: inline-block;
  background: none;
  min-width: 160px;
  margin: 0.5rem 0;
}
nav { display: flex; align-items: center; }
main {
  flex-grow: 1;
  max-width: 800px;
  margin: 0 auto;
  text-align: center;
  padding: 0.5rem;
}
footer {
  height: 80px;
  display: flex;
  align-items: center;
  background-color: var(--color-text);
  color: var(--color-background);
  justify-content: center;
  margin-top: 100px;
}

section,
.section {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  background-color: #f6f7f9;
  padding: 3rem 9rem;
  text-align: start;
}
section * {
  margin: 1rem 0;
}
h2 {
  font-size: 32px;
}
p {
  font-size: calc(var(--font-size) * 1.5);
}
input {
  font-size: 32px;
  line-height: 50px;
  border: 2px solid #222;
  outline: none;
  padding: 0 0.5rem;
}

/*
 * Utilities
 */
.flex{ display: flex;	}
.inline-flex { display: inline-flex;	}
.flex-row { flex-direction: row;	}
.flex-row-reverse { flex-direction: row-reverse;	}
.flex-col { flex-direction: column;	 }
.flex-col-reverse { flex-direction: column-reverse;}
.flex-wrap { flex-wrap: wrap;  }
.flex-wrap-reverse { flex-wrap: wrap-reverse;  }
.flex-nowrap { flex-wrap: nowrap; }
.flex-1 { flex: 1 1 0%;  }
.flex-auto { flex: 1 1 auto;  }
.flex-initial { flex: 0 1 auto;  }
.flex-none { flex: none; }
.flex-grow { flex-grow: 1;  }
.flex-grow-0 { flex-grow: 0; }
.flex-shrink { flex-shrink: 1; }