The supporter pack contains:
- STB's original soundtrack (Freely licenced tracks, mostly CC-BY)
- Game's manual, shareable
- The comic "Kiki's Masterpiece", avoid sharing it too openly
- Super Tilt Bro.'s summer playbook, share it as widely as you see fit
- A "thank you" note. This is only for supporters, I guess there is no point in sharing it :)
Most items are not explicitely freely licenced, making them legally "all rights reserved." I could go ask authors to clear the rights but keeping it exclusive to the supporter pack also has its charm. Anyway, the greatest value in the supporter pack is the satisfaction that comes with helping the game's continued development (which is not shareable by nature.)
That said, if you buy the pack, buy the game, or play the game: thank you ❤️