#tc-wrapper {
  display: flex;
  flex-wrap: wrap;
  border: 1px solid #ddd;
  border-radius: 8px;
  background: #fff;
}
#tc-sidebar {
  flex: 1 1 200px;
  background: #f9f9f9;
  border-right: 1px solid #ddd;
  padding: 10px;
}
.tc-tab {
  padding: 10px;
  cursor: pointer;
  border-radius: 5px;
  margin-bottom: 5px;
  transition: background 0.3s;
}
.tc-tab:hover {
  background: #e9e9e9;
}
.tc-tab.active {
  background: #dfefff;
  font-weight: bold;
}
#tc-content {
  flex: 3 1 600px;
  padding: 20px;
}
.tc-calculator {
  display: none;
}
.tc-calculator.active {
  display: block;
}