neat idea, flawed execution.
I like the concept, but feel there are a few things that could have used tweaking. The first and most significant is that you cannot hold a directional button to continue sliding a piece. In most recent Tetris iterations, this is a key feature that makes movement fast, simple, and easy, which allows the more strategic nature of the game to come to the forefront.
Secondly, I regularly feel cut off when turning corners. This is hard to explain verbally, but I regularly feel that once I go over a corner, I have far less room than I though I would to move down. This may not be an issue that needs to be solved with an actual tweak to core gameplay, as it's likely a challenge that can be overcome with skill, but a square outlining the orbit of your Tetrominoe would be quite helpful.
Lastly, I feel that clearing rectangles leaves behind a bit too much debris. If I form a 4x4 that happens to have an awkward extrusion, that extrusion sticks around and makes a big problem. It feels a bit like a penalty for doing exactly what I'm supposed to, which isn't great.
Other than that, I quite liked Fliptris, and I'm glad I checked it out.