Modes
Foundations has four modes: Chartory Light, Chartory Dark, Ember and Ember Light. Every token has a value in each, so switching the mode restyles every Hearth chart at once.
Light mirrors dark
Each colour family keeps its hue in both modes; only lightness moves. Neutrals come from one grey base, inverted, so a chart reads the same in light and dark.
Switch the mode
In Figma, set the Foundations mode on a frame; every Hearth chart inside follows. Presets are modes too, so a new preset never changes a component.