Invertebrate Achievement Patch

Hi all! Thanks for playing the demo — I hope you're having a good time with it :)

Two players alerted me to a bug with the invertebrate fossil achievement: despite finding 8/8 invertebrate fossils, the steam achievement was logging it as 7/8.

This patch fixes that issue, and it also should award players who have found all 8 invertebrate fossils with the achievement the next time they load their save file.

If there's any issues with this, please let me know!

Thanks for all the support, Josh