You can pledge for any "core reward" on PayPal. If you want something different, it's subject to availability. Just send us a message to confirm your reward is available, and then use the custom pledge button at the bottom of the PayPal page to enter the appropriate amount.
We want the game on as many platforms as possible, especially console and handhelds, but we don't want to bite off more than we can chew and not reach our milestones, so we're sticking to Windows (and now Mac and Linux due to stretch goal fulfillment!) for our minimum goal. If we're lucky enough to need to consider stretch goals, additional platforms are at the top of our list! We chose PS4 as our first stretch goal because that's the best information we had at the time. This does not mean we're not considering other platforms, or that the platform story ends with this Kickstarter.
Any backer who is entitled to a copy of the game will receive it for their platform of choice, based on which platforms are available (at this time, Windows, Mac, and Linux).
We love Steam! Currently, the Greenlight program only takes submissions for games that are substantially complete. When the time comes we will submit and do our best to get there. That said, we'll always offer a DRM-free version for those who prefer to have that choice.
We were really conscious of this going in. We didn't want to give something away like a weapon that unbalances the game, or an achievement that nobody else can get, but we still wanted to give backers something special for their contribution. We came up with weapon skins. These skins don't change a weapon's stats or area of effect, but they do change their look. It was our best shot at a compromise and we hope you like it. If you have feedback, get back to us!