What game actions in Riftbound can't be responded to?

Ruling: It's easier to think of what CAN be responded to: anything that makes a chain (abilities, units with triggers, and gears). The exceptions are add abilities, units themselves, and gears - these three cannot be responded to even though they use the chain.

Sequence:

• Playing a unit cannot be responded to
• If that unit has a "when I'm played" (WYPM) trigger, that ability goes on the chain and CAN be responded to

Nuances:

• Cannot respond to: tapping & recycling rune, adding mana to pool, ending turn, playing a unit with no trigger, hiding a card, beginning phase (except hold triggers), standard moving
• Might-changing effects using "While" (like Assault, Shield, or conditional might bonuses) don't use the chain
• Physical game actions like shuffling, tapping cards, or taking a drink also cannot be responded to