Sorry, I will fix that soon in an update. You will be able to choose the last level from the menu and go through it again + see the results. I forgot that itch.io doesn't have Steam achievements :/. The game first published on Steam.
Temp solution: Maybe You can use Steam? Please get free key https://itch.io/t/67604/how-to-get-a-steam-key-from-your-itchio-purchase When you run the game on Steam, the game will load the save game from the Itch.io version, so select last level and play.