[AldousHaxley]

This is fantastic. My only suggestion would be a stronger visual indication of when something gets added to the sum or the score. It probably sounds cosmetic, but visual feedback is helpful for reinforcing text explanations (at least for me, being a more hands-on learner).

[zsch]

That makes complete sense. I originally considered making a small noise when the sum was added to the score, though I'm leaning more towards flashing the updated score with a different color. Thank you for the feedback.