Strata is a simple puzzle game for Android, in which you have an N×N grid of tiles, most of which are colored. You have to place colored ribbons across all of the 2N columns and rows, choosing the order of colors and positions in such a way that the second ribbon which overlays any colored tile correctly reproduces the color of the tile. (Each tile will be overlaid by exactly two ribbons at the end, of course, one column and one row, but which one dominates depends on which you place second.)
There is no low-color-vision mode that I was able to find, which seems a bit of an oversight; even in a body with full color vision, some of the palette entries were a bit difficult to tell apart.
There's seven “sets”, increasing in length and difficulty, each of which has about four chapters, starting with a tutorial, then 2×2 and 3×3 puzzles, gradually introducing larger ones until the lengthy 6×6's come in closer to the end. Each set has different palettes, and different notes and voices for the little arpeggios that play as you place ribbons and complete puzzles; the sound is mostly the same for the first three or four sets, but then takes on some distinctly seasonal themes toward the end.
(Yes, including some of those seasonal ones. Not overtly, not in your face, but clearly related enough.)
The puzzles can have a meditative feel (if you like that) and/or get very same-y (if you don't) after a while. There isn't any twist to the mechanics that comes in, it's just more and more of them until you run out. The way to determine the solution is straightforward and repetitive once you've got the hang of it, but it does provide a nice “push things onto the stack and then pull them off in the right order” cognitive-exercise feel. If you like books of sudoku puzzles, you might like this.
We got “Perfect” on all the puzzles, which means placing all the ribbons correctly without having to retract any midstream; you do get unlimited tries for that, though I'd think writing down the answer would be cheating. You can supposedly get a hint for each puzzle if you want it (which blocks off Perfect for that puzzle, presumably forever), telling you either the order of colors or the order of positions corresponding to a solution. We never bothered; I think that would make it way too easy.
There's some slightly irritating bugs, such as achievements for sets triggering too early (on the first rather than the last puzzle completion) and some audio glitches getting all the voices to play later on. Nothing critical that we're aware of, though.
Another one retired from the queue.
Addendum: The Google Play page claims it needs access to in-app purchases, but as far as I can tell this never actually shows up; I'm guessing it's a holdover from some SDK option or perhaps from the “free” version (which I ignored, so I can't say how they differ in first person).