1.2.0 has some bug and some performance problems. The current version is 1.3.2.
If you click the "Download Now" button, you should see a popup with payment options, right above the payment amount box there is a link: "No thanks, just take me to the downloads". Click that, download "bronze-age-windows.zip", and find where it was saved. Unzip and play.
Alternatively you can use the itch.io app which makes installing really easy.