A shadow should communicate elevation or separation, not become the focal point. Start with a small downward offset, moderate blur, little or no spread, and low opacity. Preview it against the surface where the component will live; the same CSS can look heavy on light gray and disappear on dark gray.
Use the box-shadow generator to compare resting and hovered states. Keep neighboring components consistent so one card does not appear unexpectedly higher than the others. Test at normal screen brightness and in both themes if your interface supports them.
If the shadow is hard to see, a subtle border or surface-color change may communicate the edge more reliably.
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