A fine, simple project but perhaps too simple to be enjoyable to play. I think you should add all the obstacles in a single scene, not switch between several to maintain the feel of continuous motion. Splitting the game into levels usually means a crash only sends you to the beginning of the current level, which is (unfortunately) not the case here – even a single collision means game over. And perhaps increase the left/right speed and decrease inertia.
Also, the waiting period, before you reach the obstacles, is too long. Even half (third?) of the time is more than enough to acclimatise and the long wait makes every game over more painful. Not to mention being instantly kicked back to the main menu can be pretty annoying.
Finally, the 'Quit' button isn't needed in WebGL and you need to add 38 to the vertical resolution of your game if you're using the footer (alternatively you can build the game with 'Minimal' template).
This can be created in Unity in approximately an hour. It works, but I don't think there will be many people 'impressed' by the gameplay.