Overall nice game! Good application of the theme I would say. I can definitely see this going forward as a mobile game, though the controls could be junky as you are not using strict lane movement, just guessing though have to try it out.
In terms of feedback -
1. More music variation with collision sound effects is required. Maybe it is already there but I did not notice.
2. You are spawning islands in 5 lanes if I am correct. Maybe have a couple of big islands to replace 2/3/4 consecutive islands. Hope that makes sense. And in some cases, you don't have to block 4 lanes, which will bring variations in obstacles.
3. Adding a cloud/fog effect will enhance the look of the game (In my opinion). Maybe add thick fog on the side screen so you cannot see islands that are far away (on L and R sides).
4. And last but not least - !!!!POWERUPS!!!!