Very good! The controls (and in particular the jump) felt great, and I liked that the inverted evil twin a different mode, not just the direct mirroring bits.
The level design was also well done, and the introduction of mechanics were nice and smooth.
I would have liked to see some more interesting interactions with the inverted self mechanic; e.g. using the evil twin to open something, or more modes to keep you on your toes, stuff like that.
But overall, this is just an excellent platformer; well done!