Shapes on the neck.
Guitarists think in shapes, not note names. The same chord shape slides up the neck and becomes a different chord. The same scale pattern repeats across strings. The fretboard is a grid. Learn the grid, unlock every key.
Pick a root and quality. The fretboard shows where to put your fingers. Open voicings use open strings. Barre voicings are moveable — slide the shape to change the key. Hit Strum to hear the chord.
Switch to Scale Shapes mode. Every scale tone lights up across the entire fretboard. Root notes are larger. The colors follow the same degree system used across all chord tools — red is the tonic, cyan is the dominant.
Click any dot on the fretboard to hear that note. In chord mode, click Strum to hear all notes at once. In scale mode, Play Scale runs through the scale on the high E string. The audio uses the same piano samples as the rest of the theory lab.
The guitar fretboard is laid out in fourths (except between G and B, which is a major third). This asymmetry is why chord shapes change when they cross those strings. It is also why guitarists memorize shapes rather than calculate intervals.
Open chords use open strings as resonant drones. They are bright and full but locked to specific keys. Barre chords sacrifice that resonance for mobility — the index finger becomes a moveable nut.
The CAGED system names five open chord shapes (C, A, G, E, D) that connect along the neck. Each shape contains the same notes in a different position. The whole neck is five overlapping zones.
Scale shapes on guitar are visual patterns. The major scale has five box positions that tile the fretboard. Once you learn the shape, transposing is physical — move your hand, same fingers, different key.
The fretboard rewards pattern recognition over theory memorization. A guitarist who knows three shapes in all positions will outplay one who knows every note name but has not built muscle memory.