Understand CSS shadow values
A box-shadow is built from horizontal and vertical offsets, blur radius, spread radius, color, and an optional inset keyword. Text shadows use offsets, blur, and color. Adjusting the controls here updates the complete declaration instantly, so you can see how each value changes the result.
Build depth with multiple layers
Several subtle shadows usually look more natural than one heavy shadow. Combine a tight dark layer for contact with a softer, wider layer for elevation, or stack colored layers to create a glow. Reorder, duplicate, or remove layers until the effect matches the interface.