24. Accessing values in arrays, 1. Using the right items
https://gdquest.github.io/learn-gdscript/#course/lesson-24-access-array-indices/practice-ErO9L4MW.tres
We call "use_item(inventory[n])" in our function, but inventory is declared at top is "var inventory = []" which is empty. Maybe the Goals should say something about "inventory, which will be populated with the items shown in the image on the right" or something.
There is a general inconsistency where sometimes we are told about some pre-populated variable that is not shown in the code editor in some lessons, but then others show the variable (being initialized) with its values, or some where we show that the variable exist but not what values it is populated with and no clarification that it will be populated by some (hidden) code.