You are the checkout. You never move. Your rules do the work.
One rule in the wrong place turns off all the others.
Say a store has four discounts set up: 25% for wholesale accounts, 10% off a first order, free shipping over ten items, a gift box over £300. On Thursday someone adds 10% off everything for the weekend, and it goes in at the top of the list.
Only the first rule that matches runs. So everyone gets the 10% and nothing else. Wholesale lose their contract price, nobody gets free shipping, no gift boxes go out. Nothing breaks and no warning appears. The only sign is four rules that never fired all weekend.
In the game, that one mistake costs you seventeen times your takings.
The rack in the game is the rule table in the plugin.
One game per plugin.