Depth plays a crucial role in spatial design. It helps organize content and guides users' focus. Similar to the real world, distant objects can appear large and intriguing, while closer items invite users to examine them up close. It's like bringing nature into the digital realm.

To enhance the sense of realism, designers use light and shadow. Objects that emit light should cast color on nearby elements, while others should create shadows to ground them in the virtual space.

However, it's essential not to overdo depth, as it can become overwhelming. Sometimes, a subtle layering of elements works better to capture users' attention. For instance, when a pop-up appears, a gentle push back can be more effective without being too distracting.

And remember, not everything requires depth. Text in 3D can be challenging to read, so it's typically kept flat for clarity and ease of use.