I have a homebrew move I am working on for throwing improvised projectiles.

Lob

When you hurl an object at a foe from a distance, roll +DEX. On a 10+, the object soars to its mark. The enemy takes a Hit. On a 7–9, you don’t make a hit, but… Choose one from the list below.

• You make your target, but the enemy is unharmed. Their attention shifts on you.
• You miss your target, but hit something else useful to you. The GM will tell you what.

I am concerned here that letting the player choose an option might cross the line. Here the player decides what happens to their projectile even after it is out of their character’s hands. It’s not something they would know or have control over.

My secondary concern is if it is crossing the line, what does that mean for this move? In the original post from 2010, John Harper doesn’t give a very explicit explanation to what is wrong with crossing the line but does say:

"Crossing the line" isn’t the end of the world in a custom move, but it’s something to be on the lookout for. Keeping moves on the player-role side of the line will help make them sharper and stronger in play.

So I’m wondering what sort of problems might be presented by crossing the line with this move.