.flex-container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    flex-direction: row;
}

.year-box {
    width: 150px;
    height: 50px;
    margin: 10px;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #0b6ba8;
    border: none;
    color: white;
    cursor: pointer;
}

.selected {
    background-color: black;
    color: white;
}

.periode {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.periode h3 {
    background-color: #0b6ba8;
    color: white;
    padding: 10px;
    font-size: 30px;
    border-radius: 10px;
}

#selectAllBtn {
    width: 150px;
    height: 50px;
    margin: 10px;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #0b6ba8;
    border: none;
    color: white;
    cursor: pointer;
}