Blank Worker URL → explore the UI with sample cards, no writes.
◆ Card Studiomock
Select a card…
Composed preview — from fields
Drop clean base art (no text) — uploads to R2 on finalize
Current print — reference, read-only
Top: the face composed from your fields, drawn over clean art you drop (blank art background until you do). Bottom: the existing printed card — art + text baked together, so it can't be overlaid. Drop clean art to recompose.