Hi NeoxSeven, thanks for your support and for reaching out. Ultimately, I chose not to have in-app purchases in the desktop version of Just Rain because it would mean that I would have had to handle the payment/transaction myself (which is somewhat difficult), as opposed to relying on itch.io and iTunes/Google Play, which have built-in mechanisms for handling transactions safely and reliably.
With that said, if you choose to purchase the Extended Features on PC and mobile I will gladly manually refund/comp you for the cost of one of them.
Thanks again for your kind words!