Sydney's Christmas morning puzzle

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Across
  1. 2. The ratio of a circle's circumference to its diameter
  2. 4. Reaper: The entity that collects Sims' souls
  3. 6. The product of all positive integers up to a given number, denoted by n!
  4. 7. The green diamond above a Sim's head
  5. 8. The space between two intersecting lines or planes, measured in degrees
  6. 10. A square made of several rounds of crochet stitches, often used in blankets
  7. 12. The rate at which a function is changing at any given point
  8. 13. A rectangular array of numbers arranged in rows and columns
Down
  1. 1. A magical creature with the body of a horse and the wings of an eagle
  2. 3. A number greater than 1 with no divisors other than 1 and itself
  3. 5. A currency used in the game
  4. 8. A type of blanket often made using crochet
  5. 9. An object in which a dark wizard can hide a part of their soul
  6. 11. Otherworldly Sims who can abduct and visit your neighborhood