I also had trouble at first, the browser version was appearing super glitchy, in linux. But I found out later that my graphics drivers somehow stopped working and that was probably why. Also the default game size it was trying to make it was also cut off the edges of the screen and such. It took me a while to figure out how to get past the first enemy without dying since it always seemed to be waiting for me in one spot and couldn't jump over it, but I eventually figured it out. Lots of features were added to the game and it was a full playable experience. It's pretty easy to speedrun past all the enemies once you know what you are doing.