the reticle is a visual aid for the experiencer to target objects within a virtual reality environment with their gaze

The style of the reticle can vary. Common designs show the reticle as a simple dot or a crosshair.

The Google Cardboard guidelines offer this advice:

If you are concerned that displaying a reticle may reduce immersion or create unnecessary visual clutter, follow these guidelines1:

– Display the reticle only when the user approaches a target that they can activate.

– Project a light source, or design obvious hover states, for objects that the user can target.

1. ‘Interative Patterns: Display Reticle’ Google Cardboard Guidelines Website.