How can I add dark shading to an outer div but not inner div with css?

I am positioning an overlay on a webcam in my react app to show a user where to position their face. Here is my JSX:

<div className='webcam-container'>
    <Webcam
        ref={webcamRef}
        screenshotFormat='image/jpeg'
        screenshotQuality={1}
        width={360}
    />
    <div className='webcam-overlay'>
        <div className='face-position-indicator' />
    </div>
</div>

And here is my css:

.webcam-container {
    position: relative;
    width: 360px;
    height: 270px;
}

.webcam-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1;
    display: flex;
    justify-content: center;
    align-items: center;
}

.face-position-indicator {
    width: 150px;
    height: 200px;
    border: 2px solid #fff;
    border-radius: 50%;
    position: absolute;
    top: 5%;
    left: 10%;
    z-index: 999;
}

It looks fine but I would like the background outside the <div className='face-position-indicator' /> to be shaded dark, so my question is how can I add a shading only to the div with a class of webcam-overlay but not the inner div with a class of face-position-indicator?

Here’s what I’ve tried so far:

.webcam-overlay {
    ...
    background-color: rgba(0, 0, 0, 0.9);
}

.face-position-indicator {
    ...
    background-color: rgba(0, 0, 0, 0.1);
}

and:

.webcam-overlay {
    ...
    background-color: rgba(0, 0, 0, 0.9);
}

.face-position-indicator {
    ...
    background-color: transparent;
}

However both these attempts just give a dark shading to all the elements.

Interestingly if I do:

.webcam-overlay {
    ...
    background-color: rgba(0, 0, 0, 0.1);
}

.face-position-indicator {
    ...
    background-color: rgba(0, 0, 0, 0.9);
}

I get a light background on the outer div and a dark background on the inner div. But I can’t achieve the opposite effect which is what I need.

Am I missing something? Is there some kind of css trick I need to apply? Chat GPT suggested adding a pseudo-element to my webcam-overlay but this also just made everything dark.