itch.io

I am interested in purchasing the first two/three documents. However, I have the 4th edition of High Frontier. From what I understand, the documents are sold in the form of early access: does this mean that when their final versions aligned with the 4th edition of HF are released, I will be able to download the new versions for free without having to repeat the purchase?

It would be nice to be able to purchase some supplements later. For example, at the moment, I'm only interested in the core manual and the This Space Intentionally supplement.

The excerpt states that the board game's map is used. I'm curious to know if the RPG also utilizes cards.

I would like to know if it is playable solo.