Interesting idea, and looks nice. Though, I did appreciate the post-processing toggle. It wasn't obvious how to play the game. I figured you had to press keyboard buttons to interact with the pieces. Instead you have to rotate the pieces on the left, and hold and drag the mouse cursor in the play area.
I'm not sure if you had to select a piece on the left, since it sometimes didn't recognise when I had outlined a piece in the field. I also wasn't sure if the colours mattered. I tried to always select an item that was all the same colour (though, often different from the colour on the left). However, I did also work if I selected multiple colours. My advice would be to give the player a lot more feedback, and to add some instructions at the start.