/* règles générales */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: Calibri, sans-serif;
  font-size: 16px;
  line-height: 1.5;
}

/* header */
header {
  background-color: #f2f2f2;
  padding: 20px;
  text-align: center;
}

header h1 {
  font-size: 2.5rem;
  margin-bottom: 10px;
}

header p {
  font-size: 1.2rem;
  margin-bottom: 20px;
}

/* liens */
a {
  color: #007bff;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* sections */
section {
  padding: 20px;
  margin-bottom: 20px;
}

section h2 {
  font-size: 2rem;
  margin-bottom: 10px;
}

/* listes */
ul {
  list-style: none;
  margin-left: 20px;
}

li {
  margin-bottom: 10px;
}

/* responsive design */
@media screen and (min-width: 768px) {
  /* header */
  header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 40px;
  }

  header h1 {
    font-size: 3rem;
  }

  header p {
    font-size: 1.5rem;
  }

  /* sections */
  section {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
  }

  section h2 {
    flex-basis: 100%;
    margin-bottom: 20px;
  }

  section div {
    flex-basis: calc(50% - 10px);
  }

  /* listes */
  ul {
    display: flex;
    flex-wrap: wrap;
  }

  li {
    flex-basis: 50%;
  }
}