Hover the staff for a ghost note · Shift = sharp · Ctrl/Cmd = flat · click or tap to play; Shift-click a note to add it to the chord. Shift-click on the staff also applies the sharp accidental.
Accidental:
(sets piano window + clef hint; key sig untouched)
Hover or tap the staff…
Chord:—
Piano window: C3–Cb6QWERTY root: C4 (←/→ to shift)