How does Fox-Fire targeting work - does 'total might 4 or less' mean the combined might of all targets, and can it target units at multiple battlefields?

Ruling: Fox-Fire targets any number of units whose might values sum to 4 or less total (e.g., four 1-might units, one 1-might and one 3-might unit, two 2-might units, etc.). When played from hand, it can target units at any battlefield(s). When played from hidden, all targets must be at the battlefield where it was hidden.

Sequence:

• Determine if Fox-Fire is being played from hand or from hidden
• If from hand: select any number of units at any battlefield(s) whose total might sums to 4 or less
• If from hidden: select any number of units only at the battlefield where Fox-Fire was hidden, whose total might sums to 4 or less

Nuances:

• The spell can target 0 units if desired
• When hidden, Fox-Fire only costs 1 power instead of its normal cost
• The spell's effectiveness can be increased when combined with Ahri's might reduction abilities