How should 'Not So Fast' be read - does it counter (enemy spell) OR (ability that chooses friendly unit/gear), or does it counter (enemy spell or ability) that chooses (friendly unit or gear)?

Ruling: Not So Fast counters an enemy spell or ability that chooses a friendly unit or gear. Both "spell" and "ability" must be enemy, and both must choose a friendly unit or gear to be valid targets.

Sequence:

• The card reads as: "Counter an [enemy spell or enemy ability] that chooses [a friendly unit or friendly gear]"
• The "or" collapses within each bracketed group - it does not split the clause into separate effects
• Both the spell/ability must be enemy AND must target your friendly unit/gear

Nuances:

• If the card were meant to counter any enemy spell OR counter abilities that target friendly units/gear separately, it would use the "choose one:" template
• The absence of a second "an" before "ability" indicates the modifiers apply to both nouns
• This reading is confirmed by the existence of Wind Wall (which costs more and counters any enemy spell)
• Can counter spells like Singularity that target your own units
• Cannot counter Time Warp (doesn't target anything)
• Can only counter one trigger from multi-trigger abilities like Falling Star