* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Lato', 'sans-serif';
    background-image: url("bg.jpg");
    background-attachment: fixed;
    background-size: cover;
    min-height: 100vh;
}

main {
    min-height: 80vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.btn {
    display: flex;
    justify-content: center;
    align-items: center;
    color: #000;
    width: 128px;
}

.btn.android {
    background: #a4c639;
}

.btn.ios {
    background: #cccccc;
}

.btn.web {
    background: #3db9bd;
}