h1 {
    width: 100%;
    text-align: center;
}
.tabs-block-wrapper {
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-flow: column;
}
#tabs, #tabs-in {
    display: flex;
}
.tab-btn {
    width: 100px;
    height: 40px;
    font-size: 20px;
    display: flex;
    justify-content: center;
    align-items: center;
    border: 1px solid black;
    border-radius: 5px;
}
.tab-btn.active {
    background-color: blue;
    color: #ffffff;
}

#contents {
    max-width: 300px;
    width: 100%;
    height: 150px;
    border: 1px solid black;
}

.content {
    display: none;
}

.content.active {
    display: block;
}