body {
    margin: 1em;
    background-color: #000;
    transition: background-color 3s;
    font-family: "lucida grande",
        "lucida sans unicode",
        "Helvetica Neue",
        "Tahoma",
        "PingFang SC",
        "Hiragino Sans GB",
        "Source Han Sans CN Normal",
        "Heiti SC",
        "Microsoft YaHei",
        "WenQuanYi Micro Hei",
        "SimSun",
        sans-serif;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    background-color: #fff;
    border-radius: 1em;
    box-sizing: border-box;
    padding-top: 0;
    padding-left: 1em;
    padding-right: 1em;
    padding-bottom: 1em;
    box-shadow: rgba(0, 0, 0, 0.12) .25em .25em 1em .25em;
}

.container header {
    text-align: center;
    padding: 1.5em 0;
    box-sizing: border-box;
}

.container header h1 {
    margin: 0;
}

.container .description .image {
    display: flex;
    justify-content: center;
}

.container .description .image canvas {
    width: 100%;
    max-width: 30em;
}

.action-btn {
    -webkit-appearance: none;
    appearance: none;
    border: 0;
    padding: 0.5em 2em;
    font-size: 1.2em;
    font-family: "lucida grande", "lucida sans unicode", "Helvetica Neue", "Tahoma", "PingFang SC", "Hiragino Sans GB", "Source Han Sans CN Normal", "Heiti SC", "Microsoft YaHei", "WenQuanYi Micro Hei", "SimSun", sans-serif;
    font-weight: bold;
    border-radius: 0.4em;
    background-color: #e8e8e8;
    color: #111;
    cursor: pointer;
}

.action-btn + .action-btn {
    margin-inline-start: 1rem;
}

/* https://github.com/tholman/github-corners */

.github-corner:hover .octo-arm {
    animation: octocat-wave 560ms ease-in-out;
}

@keyframes octocat-wave {
    0%, 100% {
        transform: rotate(0);
    }
    20%, 60% {
        transform: rotate(-25deg);
    }
    40%, 80% {
        transform: rotate(10deg);
    }
}

@media (max-width: 1000px) {
    .github-corner {
        display: none;
    }
}