Can you float mana during your opponent's turn by tapping runes in response to an opponent's action?

Ruling: Yes, you can float mana during your opponent's turn by tapping runes in response to actions like an opponent attempting to kill your attacker.

Nuances:

• Currently runes don't have the reaction keyword, but this is acknowledged as something that will be fixed in future rules
• The ability to tap runes at reaction speed is necessary to pay for reaction-speed spells during your own turn as well
• Energy and power pools are emptied at the end of each turn and at the end of each beginning step