Sherlockkat has discovered an unfortunate bug, where in rare cases the only cave exit from a given section could be rendered inaccessible by earth collapsing directly on top of it.
As an unfair game-ending event, this demands a hotfix, but I've decided not to release a 7c because it's a mere one-line fix to the code and doesn't break seed or save compatibility, so I've instead stealth-updated the official 7b download.
If you already have Alpha 7b, to update either re-download the game and migrate as usual, or take the easier route and just download the patch
here and overwrite your 7b .exe.
(Clarification: Anyone who gets Alpha 7 via their download link after this post doesn't need to worry about updating!)Thanks for the report, Sherlockkat!
I considered releasing the other content updates I've made in the past week as a true 7c, but decided against it since that's how we got 7b and this problem in the first place--releasing some really recent work without enough final testing (if you recall I rushed the end of Alpha 7 a bit to get it out a week early).
Anyway, Alpha 8 is in the works, moving towards filling in the missing cave content. Expect to see it in April!