index.css

html, body {
    margin: 0;
    padding: 0;
    background: #1F2937;
}
#header{
    background-color: #3A69D2;
    height: 190px;
    color: white;
    text-align: center
}

h1 {
    padding-top: 50px;
    margin: 0;
}

#header p {
    /* margin-top: -20px; */
}

#main {
    /* background: #1F2937; */
    /* height: calc(100vh - 190px); */
}

#button-container {
    padding-top: 40px;
    padding-bottom: 40px;
    text-align: center;
}

#button-container button {
    color: #4A4E74;
    margin: 30px;
    padding: 9px 13px;
    background-color: #D1D4F4;
    border-radius: 7px;
    border: 1px solid gray;

}
.titles {
    color: #D5D4D8;
    text-align: center;
    padding: 0 40px;
    display: flex;
    justify-content: space-between;
}

hr {
    border: 0.5px solid #C3C6DB;
    margin: 0 40px;
}

#invoice-container{
    padding: 40px;
}
#button-invoice{
    width: 100%;
    background: #3A69D2;
    border: none;
    /* shadow/sm */
    box-shadow: 0px 1px 2px rgba(0, 0, 0, 0.05);
    border-radius: 7px;
    padding: 9px 17px 9px 15px;
    gap: 12px;
    color:#FFFFFF;
    font-weight: 500;
    font-size: 16px;
    line-height: 24px;
}

#button-invoice img{
    box-sizing: border-box;
    margin-right: 10px;
}

#items-list{
    list-style: none;
    padding: 0 40px;
    margin: 0;
}
#items-list li {
    display: flex;
    align-items: center;
    justify-content: space-between;
    color: #F5F5F5;
}

#items-list li button {
    background: none;
    border: none;
    color: #D5D4D8;
    font-weight: 400;
    font-size: 8px;
    line-height: 20px;
    text-align: center;
    position: absolute;
    padding: 0 8px;
}

#total-row {
    color: #F5F5F5;
    text-align: center;
    padding: 40px;
    display: flex;
    justify-content: space-between;
    font-weight: 400;
    font-size: 12px;
    line-height: 15px;
}

#total{
    font-weight: 600;
    font-size: 36px;
}