Remove one letter at a time. Every layer must still be a word, and some layers have rules. Dig down through geologic time to a single A or I.
Tap a letter to erode it.
Each puzzle starts with one word. Tap a letter (or type it) to remove it. The letters that remain, in the same order, must spell a word, which becomes the next layer down. Dig all the way to bedrock: a single A or I.
Some layers carry a rule, shown on the band. Weathering: only the first or last letter. Dissolution: remove a vowel. Fault: only an inside letter. Compaction: remove a consonant. Monday and Tuesday have one rule, Wednesday to Saturday two, Sunday three.
Some layers are traps: no letter can come out under the rules without breaking the word. That is an extinction event. Undo and try another line. Reach bedrock without backtracking for a clean core sample. There are 125 digs. The page opens on today's, and any dig can be played or replayed from All digs. Progress is saved in your browser.
Illustrations from game-icons.net by Lorc, Delapouite and contributors, used under CC BY 3.0. Keys: type a letter to erode it, Backspace to undo. Fonts: Alegreya and Alegreya Sans, SIL Open Font License.