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

html, body {
    width: 100%;
    height: 100%;
    overflow: hidden;
    background: #000;
}

video {
    height: 100%;
    width: auto;
    display: block;
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
}

.download-btn {
    position: absolute;
    bottom: 25%;
    left: 50%;
    transform: translateX(-50%);
    width: 270px;
    height: auto;
    z-index: 10;
    cursor: pointer;
    animation: pulse 0.8s infinite alternate;
    transform-origin: center center;
}

@keyframes pulse {
    0% { transform: translateX(-50%) scale(1); }
    100% { transform: translateX(-50%) scale(1.1); }
}