During the CD-ROM era -- that is, in the early-mid 90s, when it was thought that the CD-ROM itself was a "new medium," and people experimented with all kinds of non-game apps delivered on CDs -- there was a category of CD-ROM's called "click and wiggles." The best known of these was Just Grandma and Me, and it was aimed at kids; there were, as in graphic adventures, places to traverse and a narrative, carried in text; but nothing in the way of puzzles, particularly. Instead, clicking on screen hotspots would cause cute little animations or sound.
Windowsill is a bit like that, except that there is an element of puzzle-solving. To exit each room, you need to find a cube. Unlike a typical graphic adventure, there often is no particular logic to how the cube is found; it's a matter of trial and error. And yet, the animations are engaging enough that it doesn't seem to matter.
It is, it should be noted, a partial demo; while there are several rooms to solve, the developer asks for $3 for the remainder of the app. Since there is no particular narrative, you won't feel cheated if you end with the free content, however.