body{
    margin:0px;
}

header{
    background-color: #80808030;
    height:80px;
}

.title-name{
    font-size: 35px;
    color:black;
    text-decoration: none;
}

main{
    display: flex;/*Flexboxを有効化*/
    justify-content: flex-start;/*子要素を左寄せにする*/
    gap: 20px;
}

video{
    margin-left: 10px;
    padding:10px;
}