How to use this guitar tuner
Tune in a quiet room. Press "Start tuning", allow microphone access, then play all 6 strings, one at a time and let it ring. The big note display shows the closest pitch; the bar below it shows how far off you are. Green means within 5 cents, amber within 15 cents, red further off. Standard tuning: E2 A2 D3 G3 B3 E4, low to high.