Lines, shapes and colours

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Across
  1. 2. the boundary(边界) of a surface
  2. 4. Red, yellow and blue
  3. 6. something that has a circular（环形的） shape
  4. 8. regular (有规律的)shapes such as square and triangle.
Down
  1. 1. green, orange, and purple.
  2. 3. shapes that can be found in nature such as leaves and flowers.
  3. 5. it tells how vibrant(鲜艳的) a colour is.饱和度，强度
  4. 7. one of the seven elements of art (线条)