Tax Free Levels

This is a major rework, mainly affecting anvil costs for low levels.

Anvil Cost Rebalance

Anvil costs are now based off of player level 30 instead of level 0.

To understand what that means, say you're level 30 and the anvil cost is 15 levels.
In vanilla you would pay the XP from level 15 to level 30, which is 1080.
In previous Tax Free Levels versions, this would cost the XP from level 0 to level 15, which is 315 - the same as if you were level 15 to begin with.
While this did make the cost independent of the player level, it was also unreasonably low in many cases.
To rebalance this, anvil costs now use the same logic as the enchanting table, meaning the anvil costs will be unaffected below player level 30 - almost, see:

No Small Tax

One small tidbit about vanilla Minecraft is that paying levels doesn't actually touch the percental experience progress.
Since higher levels require more XP to reach, this means you actually not only lose levels but also a small amount of XP.
This "tax" was already dealt with for high player levels and for consistency is now also dealt with for low levels.

Git Gud

Previously this mod used the addExperience() method to pay XP, which had the funny side effect of lowering the player's score, even into the negatives! Not anymore!

Mod Compatibility (for mod devs)

Every Redirect has been changed into a more compatible option.
All Mixins were split by their function and can even be disabled by using a custom field in your fabric.mod.json (see README on GitHub).
Almost all the logic was moved in the main TaxFreeLevels class for easy access.