Something I must add about this article @Richard_Horne ; Legos patent expired, but what they did was they trademarked the Lego design, and will actively battle you legally if you try to make lego compatible bricks.
@ThantiK Thanks, that’s good to know. I see the Lego company do seem to support the fan and small ‘custom’ business - even helping them make sure the tooling is to the right spec. But sure they don’t want people just copying them for the bulk of product.
Think about it, Lego makes a product that last practically forever. So unless you loose bricks, dog or child eats bricks, or you accidently melt the bricks, you never buy new bricks! This is why they would fight to keep production in their hands and also why they constantly come out with new sets and spinoffs. And I still love them!