Back to MatrixLines: there are only 20 levels and I polished them off very quickly. I should note that the user-interface is terrible.
What's different: the last few levels have clear squares: they act both as a reflector and as being transparent. Therefore, when the light hits it, two rays emerge. Also, some squares add color to the beams which then means that some targets are red or green and must be hit with a matching ray.
The moral of the story: even bad puzzle apps that seem awful at first may end up being half-way decent.