xkcd xkcd.com xkcd.com: A webcomic of romance and math humor.Tennis Ballson April 23, 2025 at 04:00 Air Facton April 21, 2025 at 04:00 Anchor Boltson April 18, 2025 at 04:00 de Sitteron April 16, 2025 at 04:00 Tennis BallsAir FactAnchor Boltsde Sitter