:host {
    display: block;
    width: 100px;
    height: 100px;
    margin: 10px;
    text-align: center;
    position: relative;
    background: radial-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.2));
    border-radius: 50%;
    font-size: 24px;
    text-shadow: 0 2px 2px rgba(0, 0, 0, 0.8);
    vertical-align: middle;
    color: #fff;
}

#reflection {
    width: 25%;
    height: 25%;
    background: url("reflection.svg") top left no-repeat;
    display: block;
    position: absolute;
    top: 14%;
    left: 15%;
    background-size: contain;
}

#content {
    max-width: 90%;
    overflow: hidden;
    display: inline-block;
    position: relative;
    top: 50%;
    transform: translateY(-50%);
}

svg {
    position: absolute;
    top: 0;
    left: 0;
}

#svgCircle {
    transition: stroke-dashoffset 200ms;
}

:host {
    display: block;
    width: 100px;
    height: 100px;
    margin: 10px;
    position: relative;
    background: radial-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.2));
    border-radius: 50%;
    font-size: 24px;
    text-shadow: 0 2px 2px rgba(0, 0, 0, 0.8);
    color: #fff;
}

#reflection {
    width: 25%;
    height: 25%;
    background: url("reflection.svg") top left no-repeat;
    display: block;
    position: absolute;
    top: 14%;
    left: 15%;
    background-size: contain;
}

#content {
    width: 100%;
    height: 100%;
    display: -webkit-flex;
    display: flex;
    -webkit-flex-direction: column;
    flex-direction: column;
    -webkit-align-items: center;
    align-items: center;
    -webkit-justify-content: center;
    justify-content: center;
}

svg {
    position: absolute;
    top: 0;
    left: 0;
}

#svgCircle {
    transition: stroke-dashoffset 200ms;
}

Use flexbox for centering the content
Use flexbox for centering the content
