Optional ReadonlycolorRGBA8 tint (0..255), default opaque white (no tint).
Optional ReadonlyrotationStatic rotation (deg, CW). Per-feature heading adds to this.
ReadonlysizeOn-screen size in CSS px [w, h] before dpr (the shader multiplies by dpr × sizeScale).
ReadonlyuvAtlas sub-rect in NORMALISED uv [u0, v0, u1, v1] (0..1; v0 = top of the sprite).
One symbol class: an atlas sub-rect + on-screen defaults.