Can opponents play reactions (like Discipline) after the Bullet Time player has paid X Power to determine the damage amount, but before damage is dealt?

Ruling: No, there is no timing window to play reactions after the power cost is paid. The power is paid when resolving the card, and once resolution begins, there is no longer any chance to respond.

Sequence:

• Player pays 1 Energy to play Bullet Time
• Opponent has timing window to cast reactions (like Defy)
• Player pays X Power to deal X damage (during resolution)
• Damage is dealt and units die (no reaction window between paying power and damage being dealt)