Ty for the feedback! The performance is something I'll try to improve. With every new stuff added, the game is getting heavier. You could try how it plays in other browsers, Chrome for example can be slower than the rest.
Regarding the obstacle appearing problem, it's the first time I hear about it, can you try to observe when it happens, if it's conneted to something? Maybe it starts to happen later in a game when you've been playing for a while?