Short, responsive, sweet and pricey. Just some keywords to describe 10 Second Ninja. You have 10 seconds to clear a level by defeating all of the enemies. You start with some simple platforms, but a few levels later the game will introduce something new. Falling pillars and portals to name a few. It requires speed, skill and a clear head. I think I would describe the game as a puzzle platformer, even if it's more action focused than you would think. There are 5 worlds to complete, and each world has about 8 levels I think. But I think it took me less than an hour to complete all 5 worlds (ok, ok, I didn't clear every level with 3 stars) so it's pretty damn short. But man, is it good. Normally I'd say that if you enjoy a game the price doesn't really matter. But it's hard to justify the price for this game just because it's so freaking short.
So, let it be for now and grab it when it's on sale, or at least costs €5 or less.