# Design exercise: Spatial Interfaces

> Coordinate systems, anchors, tracking, depth, occlusion, hand/eye input, world understanding, and spatial UI. Implement designOutline() returning non-empty values for: coordinateSystem, tracking, spatialInteraction. Each value must name a concrete mechanism or decision.

Canonical: https://learn.significanthobbies.com/curriculum/drills/practice-spatial-interfaces

Coordinate systems, anchors, tracking, depth, occlusion, hand/eye input, world understanding, and spatial UI. Implement designOutline() returning non-empty values for: coordinateSystem, tracking, spatialInteraction. Each value must name a concrete mechanism or decision.

## The mechanism

Spatial interfaces place persistent state in a changing coordinate system. Tracking confidence, scale, depth, occlusion, ergonomics, and recovery from lost anchors are core.

## Expected evidence

A design outline with coordinateSystem, tracking, spatialInteraction plus an explicit failure mode or trade-off.

## Hints

- Name the failure mode before selecting the mechanism.

## Sources and practice

- [WebXR Device API](https://www.w3.org/TR/webxr/)
- [Study Spatial Interfaces](https://learn.significanthobbies.com/curriculum/concepts/spatial-interfaces)
- [Try the interactive drill](https://learn.significanthobbies.com/drills/practice-spatial-interfaces)
- [All practice briefs](https://learn.significanthobbies.com/curriculum/drills/)