How many targets can Piercing Light target if repeated: 2 or 4?

Ruling: Piercing Light can target 4 targets when repeated, as long as 2 of them are at a battlefield.

Sequence:

• Target 1: at a battlefield
• Target 2: anywhere
• Target 3: at a battlefield
• Target 4: anywhere

Nuances:

• The battlefield requirement must be satisfied twice (for targets 1 and 3)