Before revision:  By modifying the acquisition function's optimization, we are reliably able to present a puzzle with a bespoke difficulty for players with different skill levels in less than five iterations (for Sudoku ) and fifteen iterations ( for the simple Roguelike ), significantly outperforming simpler heuristics for difficulty adjustment in said domains, with the added benefit of maintaining a model of the user.
After revision:  By modifying the acquisition function's optimization, we are reliably able to present a puzzle with a bespoke difficulty for players with different skill levels in less than five iterations (for Sudoku ) and fifteen iterations for the simple Roguelike ), significantly outperforming simpler heuristics for difficulty adjustment in said domains, with the added benefit of maintaining a model of the user.