Deflection

You can’t make a spell which is on the stack target itself.

You choose the spell to target on announcement, but you pick the new target for that spell on resolution.

This does not check if the current target is legal. It just checks if the spell has a single target.

The target of a spell that targets another spell on the stack can be changed to any other spell on the stack, even if the new target will resolve before the spell does.

If there is no other legal target for the spell, this does not change the target.

This only targets the spell being changed, not the original or new target of the spell it is affecting.