How catalog designs become Shopify variants, and why size is a separate order-time selection—not a variant.
A variant is a purchasable SKU.
Variants are created from product type × color.
Size is chosen at order time via metafield UI.
Size affects price but does not create a new variant.
A fourth dimension — material (wallpaper substrate) — is planned.
This will add a third Shopify option, multiplying variant counts.
— This is the most important structural concept in the system.
SKU format: PM_{ABBR}_{TYPE}{COLOR:02d} — e.g. PM_KB_WP03
= Kleine beer, Wallpaper, color 03 (Mosterd). Illustrative format; actual SKUs follow this pattern.