:root {
--primary-color: rgb(33, 15, 106);
}

.timeline{
  font-family: -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Open Sans, Ubuntu, Fira Sans, Helvetica Neue, sans-serif;
  margin: 0;
  display: flex;
  flex-direction: column;
}


/* definition of vertical line */
.timeline {
  margin: 90px auto;
  width: 700px;
  border-left: 4px solid var(--primary-color);
  padding: 0 20px 0 30px;
}
.timeline::before {
  content: '';
  width: 100px;
}

/* definition of link-box */
.article-box {
  background-color: #eee;
  padding: 10px 25px;
  border: 1px solid #bbb;
  position: relative;
  margin-bottom: 20px;
  border-left: 4px solid var(--primary-color);
}

/* definition of line to link-box */
.article-box:before{
  content: '';
  display: block;
  width: 35px;
  border-top: 3px solid var(--primary-color);
  position: absolute;
  top: 10px;
  left: -35px;
}

/* definition of year-box */
h2 {
  background-color: var(--primary-color);
  color: #ddd;
  text-align: center;
  font-size: 16px;
  font-weight: 400;
  width: 80px;
  padding: 5px 5px;
  position: relative;
  margin-bottom: 20px;
  left: -120px;
}

/* definition of month-box */
h3 {
  background-color: var(--primary-color);
  color: #ddd;
  text-align: center;
  font-size: 14px;
  font-weight: 400;
  width: 100px;
  padding: 5px 5px;
  position: relative;
  margin-bottom: 20px;
  left: -30px;
}

.article_date {
  color: #333;
  font-size: 10px;
}