I love how well the flipping upside-down mechanic pairs with the hourglass theme! The timer, which subtracts or adds time depending on whether the glass is right side up or upside down is also unique--it was easy to understand that you couldn't run out of time by hitting 0 or the upper time boundary.
It took me a while to get used to the flipping. It might be because of how the camera follows the player, but it feels a little off position right after I flip. This sometimes made me bump into spikes accidentally. It's helpful that the background arrows show which direction you're facing, though, and I also liked the tips that each character would give for the next level.
Overall, the levels were trickier than I thought, but it was fun to finally figure the paths out. Love the art, theming, and the cutscenes, too!