You can no longer donate VIA Kickstarter, but you can still donate using Paypal: link
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If you donate $15 you can get a DRM-Free or Steam copy of the Digital PC, Linux, or Mac Key.
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If you donate $15 you can get the PSVita or PS4 Version.
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If you donate $15 you can get a Wii U Version.
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If you donate $15, you get the Digital Soundtrack.
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