thanks for reporting this! Yes, there is a known issue about walls just...deciding not to work. I haven't been able to replicate it, it may have something to do with the collision loading in after the game starts or something. Also, There is a way for me to get rid of the starting game screenshot, which I have done so there's no more confusion at the start haha!
THANK YOU!!! this comment was able to help me find exactly what the problem was. I have since uploaded a new version. I'm not sure if doing this with a browser game makes you lose your save file, however, but walls SHOULD work now for everyone loading in a save in the future.