The same seven pieces: how can they make different pictures?
同样七块板，怎么变出不同的图案？
七块小板放在桌上，能拼成一个正方形。
Seven small pieces on a table can fit together into a square.
换一种摆法，它们又能拼出像动物一样的图案。
Arrange them differently, and they can form a shape that looks like an animal.
小板没有变，图案怎么就变了？
The pieces have not changed, so how has the picture changed?
这就是七巧板：一套只有七块板的拼图玩具。
This is tangram: a puzzle toy with just seven pieces.
其中有两个大三角形、一个中三角形和两个小三角形。
They include two large triangles, one medium triangle, and two small triangles.
另外两块，是一个正方形和一个平行四边形。
The other two pieces are a square and a parallelogram.
平行四边形有两组对边；同一组的两条边沿直线延长，也不会相交。
A parallelogram has two pairs of opposite sides; the two sides in each pair will not meet even when extended in straight lines.
玩的时候，要用上全部七块，不把它们叠起来，拼出与样图相同的外形。
To play, you use all seven pieces without overlap to make the same outline as the example picture.
你可以移动小板，也可以转动它们，改变每块板的方向。
You can move the pieces or rotate them to change the direction each one faces.
位置和方向一变，拼出来的外边缘也可能跟着变。
When their positions and directions change, the outer outline of the arrangement may change too.
一个角可能让人想到头，另一处可能让人想到尾巴。
One corner might suggest a head, while another part might suggest a tail.
这些小板就不再只是几块三角形和四边形，而成了一个可以认出来的图案。
The pieces become more than a few triangles and quadrilaterals: they form a recognizable picture.
还有一个有意思的地方：图案变了，小板本身的大小却没变。
There is another interesting detail: the picture changes, but the pieces themselves stay the same size.
只要用的还是这七块、不叠在一起，它们在桌上盖住的总面积就一样。
As long as you use the same seven pieces without overlap, the total area they cover on the table stays the same.
这里说的是小板实际盖住的地方，不包括图案中间的空隙。
This means the space actually covered by the pieces, excluding any gaps within the arrangement.
原来，七巧板变出的新图案，来自新的组合，而不是更多的小板。
So tangram's new pictures come from new combinations, rather than additional pieces.
