I don't get it. There are only two possibilities for the tetris piece's position: I can put it so that the tetromino icon is the short end of the piece. But then the upper star is isolated without a partner and the solution is invalid. So I have to move it down by one block so that it isolates the top right square. But then I don't have a way of separating the other squares.
I'm sure there's some trickery with the colors involved, but I can't figure it out. I've recorded it with my phone so I can inspect the puzzle with different background colors. When the background is blue, the icons which are red in the screenshot disappear. But this doesn't help me because I still have to separate the purple, green and cyan ones.