1 of 7: The classic Atari video game Pong is played on the facade of the Cira Center in Philadelphia on Friday April 19, 2013. Hundreds of built-in LED lights embedded in the north face of the Cira Centre were used to replicate the familiar paddles and ball with gamers controlling giant, table-mounted joysticks across the Schuylkill River from the building. (AP Photo/ Joseph Kaczmarek)

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