* {
    box-sizing: border-box;
}

body {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

#container {
    width: 960px;
    border: 10px slateblue;
}

header {
    display: flex;
    background-color: #ccc;
    max-width: 900px;
    margin: auto;
}

.img-slide {
    position: absolute;
    right: 0px;
    bottom: 0px;
}

.img-slide-button {
    display: block;
}

ul {
    list-style: none;
}

a {
    color: 333;
    text-decoration: none;
}

article {
    border: 5px white solid;
}

.header-list > li {
    width: 100px;
    background: yellow;
    display: inline-block;
}

.nav-list > li {
    width: 100px;
    background: red;
    display: inline-block;
}

nav {
    background-color: rgb(255, 0, 149);
}

.background {
    display: relative;
    width: 960px;
    height: 400px;
    background-image: linear-gradient(rgba(0, 0, 0, 0), rgba(0, 0, 0, 1)),
        url('https://i.pinimg.com/originals/87/1b/39/871b396285ecb4e62b4803a731e3d4db.jpg');
    background-position: center;
}

section {
    background-color: skyblue;
    display: flex;
    flex-wrap: wrap;
}

section article {
    width: 320px;
}

footer {
    background-color: rgb(201, 61, 42);
    text-align: center;
}

footer aside,
footer p {
    height: 50px;
    border: 2px solid #333;
}