Difficulty Bonus:
Easy: 100 points
Medium: 200 points
Hard: 300 points
Expert: 400 points
Time Bonus:
Easy: 180 sec minus Time spent
Medium: 360 sec minus Time spent
Hard: 540 sec minus Time spent
Expert: 720 sec minus Time spent
If we spend more Time than given a certain difficulty, we have Time Bonus = 0.
Final Score = Percentage [Completing puzzle without help or errors] * (Difficulty Bonus + Time Bonus)