If you use the itch app, updates come automatically, otherwise you have to download them from the website. The current version is alpha with a lot of the main content held back. It's coming in fast now though as we inch toward beta.
so do i have to download every update seperately or do i do a download of the game main file again?
If you use the app it only installed the changes, if you download it from the website, you grab the entire game again.
How do I get the itch app?
https://itch.io/app
