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5 inventions to master first, in an order where each one only needs those before it.
The first cutting edge
Light, heat and cooked food
Clay turned to stone by fire
needs 2
Wood cooked slowly under earth
needs 1, 2
Copper and tin, harder together
needs 2, 3, 4
Chemistry that pushes a current
Goal · needs 5
Type a name, a date, a material, a domain…