header {
    text-align: center;
    margin-top: 100px
}

:root {
    --dark-green: #004400;
    --light-green:  #00ff00;
    --intermediate-green: #00aa00;
    --btn-bar-margin: auto;
    --btn-bar-color: transparent;
}

h1 {
    font-size: 60pt;
    line-height: 130%;
    color: transparent;
    -webkit-background-clip: text;
    background-clip: text;
    background-image: linear-gradient(to left, var(--light-green), var(--dark-green));
    animation: greenAnimation 3s infinite alternate, grow 12s infinite alternate;
}

h4 {
    margin-top: -10px;
    color: transparent;
    -webkit-background-clip: text;
    background-clip: text;
    background-image: linear-gradient(to left, var(--light-green), var(--dark-green));
    animation: greenAnimation 3s infinite alternate;
}

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

@keyframes greenAnimation {
    0% {
        --dark-green: #007700;
        --light-green:  #00ff99;
    }

    50% {
        --dark-green: #006600;
        --light-green:  #00ff66;
    }

    100% {
        --dark-green: #004400;
        --light-green:  #00ff00;
    }
}

@keyframes grow {
    0% {
        font-size: 60pt;
    }

    100% {
        font-size: 63pt;
    }
}

@keyframes grow2 {
    0% {
        font-size: 40pt;
    }

    100% {
        font-size: 42pt;
    }
}

@keyframes press {
    0% {
        --btn-bar-margin: auto;
    }

    100% {
        --btn-bar-margin: 40%;
    }
}

#get-started {
    background-color: var(--light-green);
    font-size: 40pt;
    margin-top: 50px;
    color: var(--dark-green);
    padding: 7.5px;
    border-radius: 15px;
    border: var(--dark-green) solid;
    box-shadow: 0 5px 0 0 var(--dark-green);
    animation: grow2 6s infinite alternate ease-in-out;
}

#get-started:hover {
    color: white;
    background-color: var(--intermediate-green);
    border: var(--light-green) solid;
    box-shadow: 0 5px 0 0 var(--light-green);
    animation: grow2 0.25s infinite alternate;
}

#get-started:active {
    animation: press 0.5s ease-out;
    --btn-bar-color: white;
}

#btn-bar {
    margin-right: var(--btn-bar-margin);
    background-color: var(--btn-bar-color);
    display: block;
}