Presentation axes

Softness is not stacking.

Depth only controls visual softness. Z-index separately controls explicit stacking order, so the two concepts do not accidentally drag each other around.

Lower stack

Still readable: z-index is independent from visual depth.

Higher stack

Blur and focus affect the whole component, including its typography.

Blur

Lower opacity, saturation and sharpness without changing z-index.

Focus

Sharp and fully saturated without automatically moving above another object.

Z-index

Stacking remains an explicit destination value.