XP Leveling Curve Designer

This is the 2D counterpart to the 3D XP Leveling Curve Designer, running the identical leveling engine — linear, power or exponential req(n) formulas, randomized session XP, and a level-up loop identical to a game backend's — while a player token climbs a flattened side-view staircase whose steps are spaced by how much XP each level actually costs. Tune the curve, watch the gaps between steps stretch into a grind wall or flatten into a trivial climb, compare curve shapes on the live req(n) graph, and read pacing stats that flag exactly when a curve crosses from "healthy" into "churn risk".