Effective at creating tension. The window for predicting whether you need to be on the left or the right is so small, especially as it appears to speed up, that you as the player get more and more focused on the game. And its when your focus is at its highest, when you've made it the farthest in the game, that it's abruptly disrupted with the jump scare. In a phrase, this game used good control over the players attention to elevate the scare.
Impressive you got this done in just a few hours. Good work!