romans.css

* {
  box-sizing: border-box;
  font-family: arial;
  color: navy;
}

.container {
  justify-content: space-between;
  align-items: stretch;
  margin: 10px auto;
  flex-wrap: wrap;
}

.content {
  display: inline-flex;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
  flex: 0 1 48%;
  width: 80%;
  padding: 25px;
  box-shadow: 0 0 3px #000;
}

.group,
.convert-output {
  display: inline-flex;
  flex: 1 1 100%;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
}

.convert-output {
  border: 1px solid #000;
  border-radius: 10px;
  background: #eee;
  min-height: 60px;
  margin: 30px 0;
  font-size: 2.2em;
}

input[type="text"] {
  width: 100%;
  padding: 10px;
  font-size: 2em;
  border: 1px solid #000;
  border-radius: 10px;
  margin-bottom: 10px;
}

input[type="checkbox"] {
  width: 20px;
  height: 20px;
}

.convert-button {
  font-size: 1.2em;
  cursor: pointer;
  border: 1px solid #000675;
  border-radius: 30px;
  padding: 10px 15px;
  background-color: #000675;
  box-shadow: 0 0 3px;
  color: #fff;
  transition: color 0.2s ease;
}

.convert-button:hover {
  color: #000;
}