.signal-background {
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    width: 100vw;
    background-color: rgba(0,0,0,0.5);
    z-index: 1000;
}

.signal-wrapper {
    position: absolute;
    display: inline-block;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.signal {
    display: inline-block;
    border-width: 8px;
    border-style: solid;
    margin-top: 10px;
    border-radius: 100%;
    height: 50px;
    width: 50px;
    opacity: 0;
    transform-origin: center;
    animation: pulsate .85s ease-out;
    animation-iteration-count: infinite;
}

    .signal.signal-dark {
        border-color: whitesmoke;
    }
    .signal.signal-light {
        border-color: #333;
    }

@keyframes pulsate {
    0% {
        transform: scale(.1);
        opacity: 0.0;
    }

    50% {
        opacity: 1;
    }

    100% {
        transform: scale(1.2);
        opacity: 0;
    }
}