The active Actor must know when they're in a threatened square, and when they leave it.
They must also know who threatens them from that square. Multiple creatures could threaten a square.
A creature threatens you if it's on a hostile team, can reach you with their melee attack, and have not yet taken a Reaction this round.
Also, the turn loop must yield to the threatening creature's reaction if they use opportunity to attack who they threaten.
Also also, maybe some warning window if you provoke opportunity, saying no cancels the Step.
Needed to close #19
The active Actor must know when they're in a threatened square, and when they leave it.
They must also know who threatens them from that square. Multiple creatures could threaten a square.
A creature threatens you if it's on a hostile team, can reach you with their melee attack, and have not yet taken a Reaction this round.
Also, the turn loop must yield to the threatening creature's reaction if they use opportunity to attack who they threaten.
Also also, maybe some warning window if you provoke opportunity, saying no cancels the Step.