The ring is a polar phase portrait. Angle is where you are in the breath cycle; distance from centre is your heart rate at that moment. One lap of the ring is one breath.
The ring starts at the top (12 o'clock) and runs clockwise, so top is the start of your inhale and the bottom is peak inhale on a 1:1 pace.
A smooth closed loop means your heart rate is doing the same thing on every breath — that's coherence, seen directly. A tangle means it isn't. The loop's orientation is phase: when its widest point sits at the bottom of the ring, heart rate is peaking with your inhale, which is resonance. As lag grows the whole loop rotates clockwise.
Older breaths are drawn fainter, so you can see the shape settle.
Coherence — the share of your heart-rate variability sitting at your breath rate. It climbs as the beat-to-beat pattern collapses into one clean wave. Above 85 is the region worth aiming for.
RSA swing — how far heart rate travels between peak and trough within one breath. This is the thing you're training.
Phase — how far heart rate trails the breath, in degrees of the cycle. Near 0° is the definition of breathing at your resonance frequency, and it settles faster than any time-domain HRV number.
Lock — how close your measured rate is to the pace you picked. Low lock with high coherence just means you've drifted to a different rate, which may well be your real resonance frequency today.
Everything runs in this tab. Heart data is never uploaded or stored — there is no server, no account, no analytics.