html {
    background: url('bg.png') #000;
    color: #fff;
    width: 100vw;
    height: 100vh;
}

main {
    height: 100%;
    width: 100%;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
}



section {
    display: flex;
    max-width: 100%;
}

.refs {
    display: flex;
    margin: 50px 0;
    flex-direction: row;
}

.refs > a {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 10px;
    filter: brightness(0.2);
    transition: .7s ease;
    
    max-width: 200px;
    max-height: 30px;
}

.refs > a:hover {
    filter: brightness(1);

}

.refs > a > img {
    display: flex;
        width: 100%;
        height: 100%;
}

@media screen and (max-width: 600px) {
    section {
        width: 100%;
        max-width: 100%;
    }
    main {
    justify-content: space-between;
  }
  
  .refs {
    display: flex;
    flex-direction: column;
    align-items: center;
}
  
  .refs > a {
    height: 120px;
    filter: brightness(0.8);
    margin: 5px 0;
    }
}