What is blue work and why does Kaspa use it for ordering?

Blue work is the metric Kaspa uses to produce a topological sort — a consistent, agreed-upon ordering — of all transactions across its blockDAG. A topological sort means that if block A came before block B in the network's history, A will always rank lower in the ordering. Blue work achieves this because of the GHOSTDAG max operator, which gives the metric the property of respecting topology. Ties between transactions with equal blue work are broken by comparing their hashes. For a beginner, the important point is that blue work is the reason Kaspa can process many parallel blocks and still know, without any ambiguity, which transaction came first.