Nothing here is a stored chart. The chord name is parsed into intervals, the intervals become notes, and every string's note is calculated from its open pitch plus the fret number in standard tuning.

Every combination of chord tones inside a hand-sized window is then tested. A shape survives if its lowest note is the root (or the slash bass), it contains every essential tone, the stretch between fingertips is under 100 mm on a 645 mm scale, and four fingers plus barres can hold it.

Survivors are ranked by effort: fingers used, stretch, barres, muted strings and how far up the neck they sit. Fret spacing on the drawing follows the real 12-tone formula, so frets close up as you move toward the body.

The key view lists the chords built on each note of the key. Richer versions (add9, m7, sus2 and so on) are only offered when every note stays inside the key. The version and shape shown first follow your stars and avoid-rules, and a coloured version is only preferred when it is about as easy to play as the plain chord.

Suggestions come from your starred shapes in three ways: sliding a shape along the neck while its open strings keep ringing, swapping one or two notes for a chord with a similar colour, and picking chords from the key your favourites share.