When playing a spell or ability, if choices are announced early (before resolution) and the opponent reacts, can the player change those choices?

Ruling: When you announce choices for a spell or ability that are normally made upon resolution, you can change those choices if your opponent reacts. However, you cannot announce choices solely to bait a reaction and then change them when your opponent doesn't react.

Sequence:

• Play the spell/ability and announce mandatory targeting choices
• Optionally announce resolution choices (like where to move a unit)
• If opponent reacts (plays something or moves units), you may change your announced resolution choices
• If opponent doesn't react, you must adhere to your announced choices

Nuances:

• You cannot use announced choices as bait - if you announce moving something somewhere to see if opponent reacts, you cannot change that choice when they don't take the bait