A war of the windows is being waged in New York City as two opposing office buildings try to one-up each other in imaginative designs made entirely of Post-it notes.

The impromptu competition on Canal Street reportedly began last week after someone used white sticky notes to spell out “HI” on an office window. Employees across the street took notice and began crafting their own Post-it murals.

The street-facing art quickly garnered attention on social media with playful images of Pac-Man, the Simpsons, Spider-Man and music references to Drake (“If You’re Reading This It’s Too Late”) and Adele (“Hello from the other side.”)

The office-supply sensation has earned a global following, with people around the world posting similar window designs under the hashtag #CanalNotes.

According to Adweek, the employees behind the Post-it art work at several advertising companies, photo agency Getty Images and other creative industries.

A similar Post-it rivalry in Manhattan emerged last December after a Santa design appeared in a window on 26th Street and Sixth Avenue.