body {
    background-color: #121212;
    color: #f7f7f7;
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    overflow-x: hidden;
}

header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: fixed;
    z-index: 1000;
    transition: top 0.3s;
    width: 100%;
    
}

.nav {
    display: flex;
    justify-content: center;
    flex-grow: 1;
}

header ul {
    display: flex;
    justify-content: center;
    list-style: none;
    margin: 0 auto;
    padding: 0;
    margin: 10px;
    width: 100%;
    align-items: center;
}

header ul li {
    margin: 0 1%;
    border: 1px solid #f7f7f7;
    border-radius: 15px;
}

header ul li a {
    color: #f7f7f7;
    text-decoration: none;
    display: inline-block;
    margin: 10px;
    padding: 2px 15px;
    position: relative;
}

header ul li a.active::after {
    content: '';
    position: absolute;
    left: 25%;
    right: 25%;
    bottom: 0;
    height: 2px;
    border-radius: 1px;
    background-color: #f76c6c;
    transition: width 0.3s ease;
    width: 50%;
}

header ul li.back {
    margin: 0 0.5rem 0 0;
    border: none;
    padding: 0;
  }
  
  header ul li.back a {
    padding: 0;
    margin: 0;
    display: flex;
    align-items: center;
  }

  header ul li.back img {
    display: block;
    width: 44px;
    height: auto;
  }