Fill a clear tumbler to the rim with pebble ice so the layers show through the glass.
Pour the strawberry syrup over the ice and let it sink before the soda goes in.
Tilt the glass and pour the lemon-lime soda slowly down the side, stopping when the fizz reaches close to the rim and settles.
Pour the half-and-half over the back of a spoon so it blooms through the pink soda in visible streaks.
Stir once with a straw to swirl the color through the glass, then notch the strawberry half onto the rim and serve right away.
Good to Know
No strawberry syrup in the house? Blend a half cup of fresh strawberries with a tablespoon of sugar and strain it; one tablespoon of that puree stands in perfectly.