[Ebree]

Could you do this with circle or sinusoid, but maybe adding a line or top & bottom point, for regular breathing?

I'm also planning to combine 40Hz bineural beats, pink noise and using drum beats per minute to keep breathing pattern without visuals.

Hmm Maybe adding more beats but of different volume or with irregular interval would produce a mental circle following path between top and bottom, breath in / breath out.

I was experimenting with small breaths sequences, like hardcoding counting without need for counting consciously but disrupting smooth breathing makes it unnatural & ineffective.