These conditions build on what the reader has discovered: the characters they met and the inventory items they obtained. They give weight to findings — an item picked up early can open a door much later.
# Character unlocked
The choice is only offered if the reader has already met a given character (unlocked in their contacts). Parameter: the required character.
Example
You can only "Ask the witness for help" if you crossed paths earlier in the investigation. Readers who missed the encounter will have to find another way.
# Item unlocked
The choice is only offered if an inventory item has been discovered. Parameter: the required item. Combine it with its negation (NOT) to offer an alternative path to those who don't have it.
Example
The manor door only opens if the rusty key is in the inventory. Without it, there's still the cellar window — riskier.
# GPS zone (on location)
Put it on a forced-progression link: the reader auto-advances to the target step when they enter (or leave) a geographic area — a point on the map + a radius. Proximity is computed on the reader's device; their position is never sent to the server. GPS tracking only starts on a step that carries such a zone (no permanent tracking). Pair it with a GPS event (which sends an email, later plays audio…) when you want an action without changing step.
Example
Arriving at the old chapel (50 m radius), the reader moves to the discovery scene on their own — no tap needed.