Make a GIANT greeting card out of a big cardboard box, (such as the type used to pack a refrigerator).

用一个大纸板箱做一张巨型贺卡，(例如用来包装冰箱的纸板箱)。

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A black card is just a regular cardboard paper. The key point is the color black. Black absorbs light. Therefore, the camera will not capture the black card.

黑卡，就是一般的纸，重点是要黑色，黑色会吸光，如此相机才不会拍摄出这片卡的颜色。

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