Damage calculator.

Sorry, I kind of forgot about this topic. I tried to downgrade to version 3.5, but it didn't work out at first; there were some issues, and I gave up. I'll try to look into it again when I have time.

Also, thanks to a good guy from the sk2tv chat, support for HP art will be added in the coming days (including collection calculation), which is sometimes needed. Open source rules!