Chapter 3
40 shirts in 5 colours and 4 sizes. Do I make 800 products?
No — you describe the shirt once, and describe colour and size as two things any shirt can have; the system builds every real combination for you.
A colour and a size are not separate products, they are properties — the same idea whether it is a shirt's size or a paint's shade. You define the shirt once, list the colours it comes in and the sizes it comes in, and ask the system to generate the combinations; asking again later, after you add a colour, only creates what is genuinely new and leaves everything else untouched.
What this buys you, and what still needs deciding per size
Stock, price and barcode are tracked per combination, because a shop can be out of medium while full of large — but you are not maintaining eight hundred separate product records to get that; you are maintaining one shirt with two lists attached to it.
What can wait: you do not need every colour and size decided before your first sale. Start with what you actually have on the shelf today, and add more combinations the day you actually stock them — a combination nobody has ever held any of is not a product you need yet.