Linear Levels
This mod has been merged with the Train's Tweaks mod under the Experience feature for versions 1.21 and above.
LinearLevels provides five different configuration options that allow you to customize the experience curve in your game according to your preferences. All configuration parameters are accessible through ModMenu or similar mods. Requires Cloth Config API to function.
In standard mode, each new level requires only 10 experience points (this is significantly less than in the vanilla version, so it's recommended to adjust the value to your liking).
Curve mode is also available, which uses the formula: XPToNextLevel = (baseXPForOneLevel + (experienceLevel * curveModeMultiplier)). By default, this mode offers a more balanced progression that doesn't become excessively difficult after level 30, unlike the original game.
(Yes, the name Linear Levels isn't entirely accurate in this case, I know)
For exact numbers for both modes and comparison with the vanilla system on a graph, see this Google Sheet.
Version 1.1.0 added an additional configuration option: level cap. It's disabled by default, but when a value is set, the experience required for the next level will stop increasing after the specified level.
Frequently Asked Questions
How will this work with XP storage mods? It depends on how those mods work. In other words, I don't know. The only thing this mod does is mixin to one method in the player entity.