header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 200px;
    background: linear-gradient(to bottom, #000000 40%, #0560aa 80%, #7cd4ef 100%);
}

body {
    padding-top: 200px;
}

.launch-button {
    position: absolute;
    left: 50%;
    top: 75%;
    transform: translate(-50%, -50%); /*account for center*/

    text-decoration: none;
    background-color: #aa0000;
    color: white;
    font-size: 20px;
    padding: 15px 60px 15px 30px;
    border-radius: 10px;

    transition: transform 0.5s, background-color 0.1s, padding 0.5s, box-shadow 0.1s;
    /*transition from one state to another; list of properties to transition with a duration*/
}

.launch-button:hover {
    background-color: #cc0000;
    box-shadow: 0 0 8px #ff0000;
}

.launch-button:active {
    background-color: #750000;
    box-shadow: 0 0 2px #750000;
    transform: translate(-50%, -20%) scale(0.7);
    padding: 15px 30px;
}

.launch-button .rocket {
    position: absolute;
    top: 50%; /*centers vertically*/
    right: 40px;

    transition: transform 0.5s;
}

.launch-button .rocket i {
    position: absolute;
    top: 0;
    left: 0;
}

.launch-button .fa-rocket {
    transform: translate(-50%, -50%) rotate(-45deg);
}

.launch-button .fa-burn {
    transform: translate(-50%, -15%) rotate(180deg) scale(0.1);
    /*center horizontally, hang lower vertically, rotate and make smaller*/
    color: orange;

    transition: transform 0.4s;
}

.launch-button:hover .fa-burn {
    transform: translate(-50%, -15%) rotate(180deg) scale(0.4);
}

.launch-button:active .fa-burn {
    transform: translate(-50%, 25%) rotate(180deg) scale(0.8);
}

.launch-button:hover .rocket {
    transform: scale(1.3);
}

.launch-button:active .rocket {
    transform: rotate(-15deg) translate(60px, -140px) scale(3.5);
}

.label {
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: white;
}

.label:hover {
    color: orange;
    text-shadow: 0 0 3px rgb(251, 255, 0, 0, 0.5);
}

.launch-button .label {
    transition: color 0.2s, text-shadow 0.2s;
}

@keyframes burn {
    from { transform: rotate(-7deg); }
    33% { transform: rotate(4deg); }
    66% { transform: rotate(-4deg); }
    to { transform: rotate(7deg); }
  }
  /*set of keyframes with the name burn. The keyframes define a series of changes to a property or set of properties*/
  /*apply keyframes to an element - chose icon ::before pseudoclass so we don't affect actual icon's transform*/
.launch-button:active .fa-burn::before {
    display: block; /*needs this to animate*/
    transform-origin: center bottom; /*apply transform around an axis at base of flame instead of center*/
    animation-name: burn; /*which keyframes to use*/
    animation-duration: 0.1s; /*duration of loop*/
    animation-iteration-count: infinite; /*loop without end*/
    animation-direction: alternate; /*keyframes alternate backwards and forwards in time*/
}