Historical Rules · 14 April 2023
Rule 702.44a
Official source text from the 14 April 2023 Rules release
Sunburst is a static ability that functions as an object is entering the battlefield. “Sunburst” means “If this object is entering the battlefield as a creature, ignoring any type-changing effects that would affect it, it enters the battlefield with a +1/+1 counter on it for each color of mana spent to cast it. Otherwise, it enters the battlefield with a charge counter on it for each color of mana spent to cast it.”