A rules engine for MTG, the most complicated card game ever made. In case you want to read the full rules (you don’t - it’s over 300 pages of tiny text), here they are: https://magic.wizards.com/en/rules
Important: The server may take some time to start back up after it hasn’t been accessed for a while. If it isn’t reachable wait 2min or so and try again. Also you must use http Service that can track the prices of some local grocery stores. Beware, the products and the legal notice are all in german and prices are in euros. I wonder how they compare to prices elsewhere?
Kinda self-explanatory, no?