I’ve been trying to make a table with a timeline on the side to make a gantt chart,

and I tried editing this

:root {
  --white: #fff;
  --divider: lightgrey;
  --body: #f5f7f8;
}

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

ul {
  list-style: none;
}

a {
  text-decoration: none;
  color: inherit;
}

body {
  background: var(--body);
  font-size: 16px;
  font-family: sans-serif;
  padding-top: 40px;
}

.chart-wrapper {
  max-width: 1150px;
  padding: 0 10px;
  margin: 0 auto;
}


/* CHART-VALUES
–––––––––––––––––––––––––––––––––––––––––––––––––– */

.chart-wrapper .chart-values {
  position: relative;
  display: flex;
  margin-bottom: 20px;
  font-weight: bold;
  font-size: 1.2rem;
}

.chart-wrapper .chart-values li {
  flex: 1;
  min-width: 80px;
  text-align: center;
}

.chart-wrapper .chart-values li:not(:last-child) {
  position: relative;
}

.chart-wrapper .chart-values li:not(:last-child)::before {
  content: '';
  position: absolute;
  right: 0;
  height: 510px;
  border-right: 1px solid var(--divider);
}


/* CHART-BARS
–––––––––––––––––––––––––––––––––––––––––––––––––– */

.chart-wrapper .chart-bars li {
  position: relative;
  color: var(--white);
  margin-bottom: 15px;
  font-size: 16px;
  border-radius: 20px;
  padding: 10px 20px;
  width: 0;
  opacity: 0;
  transition: all 0.65s linear 0.2s;
}

@media screen and (max-width: 600px) {
  .chart-wrapper .chart-bars li {
    padding: 10px;
  }
}


/* FOOTER
–––––––––––––––––––––––––––––––––––––––––––––––––– */

.page-footer {
  font-size: 0.85rem;
  padding: 10px;
  text-align: right;
  color: var(--black);
}

.page-footer span {
  color: #e31b23;
}
<div class="container">
  <div class="chart">
    <div class="chart-row chart-period">
      <div class="chart-row-item"></div>
      <span>January</span><span>February</span><span>March</span>
      <span>April</span><span>May</span><span>June</span>
      <span>July</span><span>August</span><span>September</span>
      <span>October</span><span>November</span><span>December</span>
    </div>
    <div class="chart-row chart-lines">
      <span></span><span></span><span></span>
      <span></span><span></span><span></span>
      <span></span><span></span><span></span>
      <span></span><span></span><span></span>
    </div>
    <div class="chart-row">
      <div class="chart-row-item">1</div>
      <ul class="chart-row-bars">
        <li class="chart-li-one">Planning</li>
      </ul>
    </div>
    <div class="chart-row">
      <div class="chart-row-item">2</div>
      <ul class="chart-row-bars">
        <li class="chart-li-two-a">Meeting</li>
        <li class="chart-li-two-b">Analysis</li>
      </ul>
    </div>
    <div class="chart-row">
      <div class="chart-row-item">3</div>
      <ul class="chart-row-bars">
        <li class="chart-li-three">Design</li>
      </ul>
    </div>
    <div class="chart-row">
      <div class="chart-row-item">4</div>
      <ul class="chart-row-bars">
        <li class="chart-li-four">Development</li>
      </ul>
    </div>
    <div class="chart-row">
      <div class="chart-row-item">5</div>
      <ul class="chart-row-bars">
        <li class="chart-li-five">Testing</li>
      </ul>
    </div>
    <div class="chart-row">
      <div class="chart-row-item">6</div>
      <ul class="chart-row-bars">
        <li class="chart-li-six">Maintenance</li>
      </ul>
    </div>
    <div class="chart-row">
      <div class="chart-row-item">7</div>
      <ul class="chart-row-bars">
        <li class="chart-li-seven">Meeting</li>
      </ul>
    </div>

  </div>

</div>

https://codepen.io/tutsplus/pen/ZEzerNB

to make the timeline on the side and make the tasks horizontal,

I couldnt make it, can someone tell me what should I edit to make it vertical?

or is there a better way to do this?