What are the four rules for a tangram?

The four rules for a tangram are:

1. All seven pieces (tans) must be used to form a specific shape or figure without overlapping.
2. The pieces cannot be resized or altered; they must remain in their original shapes.
3. The arrangement of the pieces should create a silhouette or outline that clearly represents the intended figure.
4. The pieces can be rotated and flipped but must maintain their original orientation without distortion.