Link: https://slappygig.github.io/oldprodigy/1-11-0/
1. To save your progress you are going to have to download it to your computer. Don't worry it's easy and when you come back just click "load character," select your save file and you're good :3
2. You don't have to do math!
3. It's offline and all the other wizards are NPCs, unfortunately you can't play with anyone </3
4. Membership is free and you can toggle it on/off in the settings anytime! :D