.topbar{
  position: fixed;
  top: 0; left: 0; right: 0;
  height: 126px;          
  background: #F4F1ED;
  display: flex;
  align-items: center;
  padding: 0 48px;
  z-index: 9999;
  box-shadow: 0 1px 0 rgba(0,0,0,0.08);
}

.nav{
  display: flex;
  gap: 34px;
  align-items: center;
}

.btn{
  position: relative;
  display: inline-block;
  background: transparent;
  color: #26244B;
  text-decoration: none;

  font-size: 18px;
  font-weight: 500;
  letter-spacing: 0.02em;

  padding: 3px 2px;
}

.btn::after{
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0px;
  height: 1px;
  background: currentColor;

  transform: scaleX(0);
  transform-origin: left;
  transition: transform 220ms ease;
}

.btn:hover::after{
  transform: scaleX(1);      /* underline draws left -> right */
  transform-origin: left;
}

.btn:not(:hover)::after{
  transform-origin: right;   /* underline disappears left -> right */
}