Yes, some serious maths required...!
Well, lifeschool has made some headway into this. Here's what he posted on Lemon:
First Samurai - Perhaps this one needs more explanation. At the end of each level completed you'll get a screen showing some stats. Here is a screenshot taken from the end of the longplay on youtube (I have no intention of watching the longplay!).
Score: 1,015,748
Your score is based on the stats of the previous level, unless you complete the game. The Level you reached + your time:
e.g.
Level 10 = 1 million (in this case + 015,748)
Level 9 = 2 million
Level 8 = 3 million
Level 7 = 4 million
Level 6 = 5 million
Level 5 = 6 million
Level 4 = 7 million
Level 3 = 8 million
Level 2 = 9 million
Level 1 = 10 million
Died on level 1 = 11 million minus your score
While playing the game, take a screen grab at the end of each level. When you die, quit the game and load up an art package. If you pressed Print Screen, simply Paste the screen grab you last took into the package. If you saved an image, you'll have to find the latest. If you use a digital camera, please take a photo at the end of each level and post the most recent.
If you cant make it to the first stats screen, perhaps take a screenshot in game. Your score is then based on 11 million minus the actual score you made in the game (lowest score wins). So if you scored 1k it would be 10,999,000. If you scored 1 point it would be 10,999,999?