David: Many of you will have seen the Pong game where essentially a single rectangle moves up and down where a ball bounces off it, or a pair of them so two people can play against each other.

大卫：你们中的许多人都曾玩过弹球游戏，这个游戏就只有一个方块上下移动，接住反弹来的球。如果两人玩时，就会出现一对方块，可以进行对抗赛。

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