Spectraball
That was easy. After playing through what may be the shortest playable demo ever (four tutorial levels and two actual game levels), I'm now reconsidering dropping a measly $10 on Spectraball. The game mechanics are just as I'd hoped they would be, but Flashcube took the gameplay in a direction I really don't like: rather than go the Metroid Prime route and use the ball mode to find items and solve puzzles - emphasizing paced exploration - Spectraball's goal is to finish a stage as quickly as possible - emphasizing falling off the map.
Though there are glowing orbs (literally, "glorbs") to collect, and there's a remote chance that later stages incorporate some sort of puzzle dynamic, the game is, very clearly, primarily about going as fast as possible. There are even leaderboards for level completion speed; which, when the top times for the two demo stages are each under four seconds, seems pretty pointless.
Well, fuck.
Progress: Gave Up -- Finished ultra-short demo