Fire Emblem Battle Calculator
It keeps track of level, stats, HP and does all the battle calculations and gives reports. You make two characters and go to fight, equip weapons etc and click through the regular FE battle preview screen and so on.
Anyone can roll fights with any characters, but to save them there is a permissions system which depends on the character, game and user.
A character belongs to none or one game. A game can belong to multiple users.
Only people who own the game that a character belongs to can modify that character, but if a character belongs to no game then anyone can save after fights with the character.
Formulas are from FE7.