body {
    font-family: "Trebuchet MS", Helvetica, sans-serif;
    text-align: center;
    color: rgb(255, 255, 255);

    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    cursor: default;

    min-height: 100vh;
    margin: 0;
    padding: 0;

    display: flex;
    flex-direction: column;
}

.header, .footer {
    background-color: rgb(30, 30, 30);
}

.wrapper {
    background-color: rgb(22, 122, 198);

    display: flex;
    flex: 1;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

/* source: ["Solved by Flexbox": https://philipwalton.github.io/solved-by-flexbox/] */
.align-top {
    align-self: flex-start;
}

.align-bottom {
    align-self: flex-end;
}

/* source: ["How TO - Alerts": http://www.w3schools.com/howto/howto_js_alert.asp] */
.alert {
    width: 960px;
    max-width: 100%;

    margin: 0 0 15px 0;
    padding: 20px 0 20px 0;
}

.alert-info {
    background-color: rgb(75, 176, 79);
}

.alert-error {
    background-color: rgb(244, 67, 54);
    display: none;
}

.close-btn {
    font-weight: bold;
    font-size: 22px;
    line-height: 20px;
    cursor: pointer;

    transition: 0.3s;
    margin: 0 30px 0 0;
    float: right;
}

.close-btn:hover {
    color: rgb(0, 0, 0);
}

#playground {
    background-color: rgb(255, 255, 255);
    max-width: 100%;

    flex: 1, 0;
}

.hud {
    background-color: rgb(30, 30, 30);
    width: 960px;
    max-width: 100%;

    display: flex;
    flex: 1, 0;
    flex-direction: row;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
}

.hud-cell {
    margin: 0;
    padding: 0;

    flex: 1;
}

/* Inspired by: ["GitHub Corners": http://tholman.com/github-corners/] */
.octocat:hover {
    background-color: rgb(64, 64, 64);
}

.octocat:hover .octo-arm {
    animation: octocat-wave 800ms ease-in-out;
    animation-iteration-count: infinite;
}

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

@media only screen and (min-height: 840px) {
    .alert {
      display: none !important;
    }
}

@media only screen and (max-height: 840px) {
    .alert {
        width: 640px;
    }

    #playground {
        width: 640px;
    }

    .hud {
        width: 640px;
    }
}

@media only screen and (max-height: 480px) {
    .alert-info {
        display: none;
    }

    .alert-error {
        display: block;
    }

    #playground {
        display: none;
    }

    .hud {
        display: none;
    }
}