Levittown was drawn in curves, and every curve is a front lawn — small, open to the sidewalk, with nowhere to hide a missed corner. Emerald Lawn Care of Long Island Inc. keeps those yards on a weekly rhythm through the season: mowing, trimming around the stoop and the fence line, edging the concrete until the border between walk and grass is one clean stroke. Summer arrives humid off the South Shore, and a lawn cut at the right height in July is the lawn still holding its color in August. By November the maples the first owners set out are letting go block after block, and the cleanup runs house to house until the yards are bare and tidy. The reward is Saturday morning: a homeowner steps out with coffee and finds nothing left to do.