Nicely done! I love the fade in/out when you switch the music on and off: that's a very nice touch.
It would be nice if the Space key would select menu items and restart the game after you die instead of having to use Enter.
I had a lot of trouble training myself which side to be on at the end of the platforms. That felt backwards to me for some reason. I think I wanted to "jump" through and "up" to the next platform, instead of just waiting to fall off the end? It always felt like the next platform was too far away and that you'd fall through the gap if you just ran off the end, so maybe a subtle jump/ramp shape at the end of the platforms would help? Or maybe it's just me.
But yeah. A fun infinite runner and lots of nice polish.