I went to the first level where you speed is halved, after finishing it (but before pressing E to go the next level) I waited in front of the door to do something else (IRL). When I came back on my computer I had a text at the bottom of the screen, explaining what to do if I'm stuck, and the game had frozen. My whole browser was super slow, I had to close the game and then my browser was responsive again (Firefox 152.0.6 on CachyOS).
Anyway, the levels that I did were fun, and I think the concept is really cool, great job! It looks you keep adding new mechanics so you don't get bored, I felt it was the right pace. And the game looks good!