3 Lines of Code Fixed 123 Failed PPO Experiments by Changing Reward Shaping
mikeysce · reddit · 2026-08-04
While training an AI to play Atari Breakout using PPO, a developer found that models consistently converged on memorized action scripts rather than reactive ball-tracking.
After 123 failed experiments, the author realized the fix wasn't more environment engineering, but reward shaping. With just three lines of code, they introduced a tiny bonus (0.05 per frame) rewarding the paddle for horizontal proximity to the ball during its descent.
This directed the optimization pressure unambiguously towards tracking, successfully breaking the model's reliance on scripted actions. The author open-sourced the project, including all failed attempts, and built a visualization tool to demonstrate the reactive policy.
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