Can you tap runes for energy during an opponent's turn (e.g., during a showdown) and float that energy until end of turn, even if you don't use it immediately?

Ruling: Yes, you can tap runes for energy at Reaction speed during an opponent's turn, and that energy will float until the turn ends.

Nuances:

• There is generally no strategic reason to float energy preemptively since having readied runes provides the same bluffing potential
• Floating energy only matters if you need to pay power but only have readied runes available (as of the current rules)