header {
    padding: 1px;
    text-align: center;
    background: #1abc9c;
    color: white;
    font-size: 30px;
}

nav {
    background: #333;
    padding: 10px 0;
}

#content{
    width: 648px;
    margin: auto;
}


.menu, .menu ul{
    line-height: 1;
    margin: 0;
    padding: 0;
    list-style-type: none;
}

.menu{
    display: block;
    position: relative;
    height: 47px;
    width: 100%;
    background: #fff;
    top: 10px;
    border-radius: 5px;
}
.menu ul>li {
    display: block;
    position: relative;
    float: left;
}

.dropdown{
    display: none;
}

.menu li>a{
    display: block;
    color: #000;
    padding: 16px;
    width: 130px;
    text-align: center;
    font-size: 15px;
    font-weight: 300;

    transition: all 0.5s ease;
}
.menu li:hover>a{
    background: #555;
    color: #fff;
}

.dropdown{
    /*  display: none;*/
    display: block;
    position: absolute;
    opacity: 0;
    background: #ccc;

    transition: all 0.3s ease;
}

.menu li:hover>ul{
    top: 47px;
    left: 0;
    opacity: 1;
}

nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
}

nav li {
    margin: 0 15px;
}
div.flex-container{
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
    gap: 10px;
    margin: 10px 5% 5% 5%;
    background: #f8f9fa;
    padding: 10px;
    border-radius: 10px;
}

div.flex-container > div{
    flex: 1;
    margin: 10px;
    border: 2px #e74c3c solid;
    padding: 10px;
    border-radius: 5px;
    background: #ffeaa7;
}

nav .nav-link {
    color: white;
    text-decoration: none;
    padding: 10px 15px;
    border-radius: 5px;
    transition: background 0.2s;
}

nav .nav-link:hover {
    background: #555;
}

footer {
    position: relative;
    left: 0;
    bottom: 0;
    width: 100%;
    background-color: #333;
    color: white;
    text-align: center;
    padding: 15px 0;
}

h1 {
    font-size: 2.5em;
    margin: 10px 0;
    color: #333;
}

h2 {
    font-size: 2em;
    margin: 18px 0;
    color: #444;
}

h3 {
    font-size: 1.5em;
    margin: 16px 0;
    color: #555;
}

h4 {
    font-size: 1.2em;
    margin: 14px 0;
    color: #666;
}

h5 {
    font-size: 1em;
    margin: 12px 0;
    color: #777;
}

h6 {
    font-size: 0.9em;
    margin: 10px 0;
    color: #888;
}