Amazing. Truly, a great simple game. Unforgiving though. It is a small finished product, the only thing that could be improved is the audio, quite repetitive. Now I am interested how someone good at it plays it. Well done.
Edit:
I think the combo count should be there all the time, it should be well visible as I need to plan whether I should move back to the island. Also, make the combo reset when touch the ground, so player gets more points for constantly being in the air.
Edit2:
Also, I think you should be able to jump after the slash, as slashes are limited and jump kinda helps to move around. Anyway, just some quick thoughts.