The first challenge of Advent of Code 2025 presents a number line puzzle from 0 to 99, where instructions rotate a cursor left or right. The key is handling modular arithmetic for large rotations, like an `L888` instruction, which requires using modulo 100 to find the final position efficiently. A developer's initial solution for Part 1 passed after debugging a ternary operation.

Part 2 intensified the problem by making the number of full rotations critical. The developer's first attempt failed because it miscounted passes across zero for large instructions. The puzzle demands tracking both the cursor's final position and the total times it crosses the starting point, a subtle but crucial distinction in the logic.

After significant troubleshooting with edge cases—like rotations perfectly divisible by 100—the developer refined the algorithm. The final solution correctly increments the password for each hundred in large instructions and properly handles left rotations crossing zero. This two-part problem, while a Day 1 challenge, required careful attention to detail and iterative debugging to secure both gold stars.