EVERSION / Zaratustra Productions / PC
It's tough to write reviews about games built on surprises, because there isn't much you can say without ruining the surprise. In the case of Eversion, even mentioning that there's a surprise lessens the experience! It's really almost necessary to do at least a little spoiling, though, because at least for the first few minutes or so of gameplay, Eversion looks like nothing more than a competent but bland cutesy platformer in the vein of Mario.
I guess the H.P. Lovecraft quote at the very beginning should probably tip you off that there's something more going on here, though. Vets of NES obscurity Monster Party - to which this game probably owes at least a small debt of inspiration - will also likely have a sense of what's coming.
You control this little flower dood, who can jump and stomp on the heads of most enemies for a little boost a la Mario. The only other button used/ability is the "eversion", which is done at certain points where you notice the background and music warping. "Everting" a level changes everything about it - solid clouds might become empty, living trees blocking a path shrivel up, formerly harmless plants turn into spiked death, etc.
The game itself is on the short side and lasts maybe only an hour, but there's some replayability in collecting all the optional gems for each level, which unlocks a bonus level at the end of the game and some possible alternate endings.
That's all the more I really want to say about the game, other than that the play control and level design is very solid. And to recommend it highly. It's really best experienced knowing as little as possible going in, however.