Переключите Профиль Терминала GNOME с командной строки

.heading {
    display: inline-block;
    font-family: "Montserrat";
    font-weight: lighter;
    text-align: left;
    margin-left: 20vw;
    line-height: 30vw;
}

body {
    width: 100%;
    margin: auto;
    font-family: 'Montserrat', sans-serif;
    background-color: white;
}

.container {
    display: flex;
    flex-wrap: wrap;
    flex-direction: row;
    justify-content: center;
    margin-top: 30px;
    flex-flow: row wrap;
    margin-top: -10vw;
}

img {
    /* margin: 9px;
  transition: filter 0.2s;
  filter: brightness(100%);
  display: inline-block;
  min-height: 100px;
  height: 50vh; */
    max-width: 100%;
}

img:hover {
    filter: brightness(80%);
}

.responsive:hover {}

header {
    position: relative;
    height: 50vh;
    background-image: linear-gradient(rgb(50, 50, 50), rgb(30, 30, 30));
    margin-top: -20px;
    transform: skewY(-5deg);
    transform-origin: top left;
}

.fullwidth {
    width: 100%;
}

.headertitle {
    margin-top: -36vh;
    margin-left: 12vw;
    position: absolute;
    font-size: calc(13px + 2.5vw);
    color: white;
    font-family: 'Montserrat';
    font-weight: lighter;
}


/* navbar */

nav {
    background: rgb(52, 52, 52);
    position: relative;
    z-index: 1;
    height: calc(40px + 6vh);
    box-shadow: 0 3px 3px -1px rgba(0, 0, 0, 0.065);
    overflow: auto;
    width: 100vw;
    display: flex;
}

nav ul {
    margin: 0;
    padding: 0;
    text-align: left;
    margin-left: 1.2vw;
}

nav ul li {
    display: inline-block;
    list-style: none;
    font-size: 1.2em;
    padding: 1vh;
}

.navul a {
    text-decoration: none;
    color: white;
    line-height: 5.5vh;
    height: 5.5vh;
    font-size: calc(15px + 0.25vh + 0.15vw);
}

.navuul a:visited,
a:link,
a:active {
    text-decoration: none;
    color: white;
    font-weight: 200;
    line-height: 5.5vh;
    height: 5.5vh;
}

.navuul a:hover {
    text-decoration: none;
    color: grey;
    font-weight: 200;
    line-height: 5.5vh;
    height: 5.5vh;
}

.submit {
    float: right;
    margin-right: 1.5vw;
}

.submit a {
    color: white;
    border-radius: 5px;
}

.navimgdiv img {
    max-width: 50px;
}

.navimgdiv {
    padding: 5px 0;
}

<div class="fullwidth"></div>
<nav>
    <a class="navimgdiv"><img src="https://cdn.worldvectorlogo.com/logos/react.svg"></a>
    <ul class="navul">
        <li><a href="#">Lumastock</a></li>
        <li><a href="#">Photos</a></li>
        <li><a href="#">Featured</a></li>
        <li><a href="#">Contact</a></li>
        <li><a href="#">Pricing</a></li>
        <li><a href="#">Assesment Requirements</a></li>
        <li class="submit"><a href="#">Submit a photo</a></li>
    </ul>
</nav>
<header></header>
<h1 class="headertitle">Image Gallery</h1>