QC is really, REALLY bloody easy. I spent more time walking through the repeated-a-million-times between level corridor than actually doing any puzzles.
The hardest puzzle in the game is
ZOMG Spoiler! Click here to view!
Making a staircase six cubes high in the penultimate room. You pick up cubes and drop them in a staircase shape.
You're shown how to execute a certain type of action, and then you do it exactly like as you were told over and over again. It's all tutorial and no puzzle. IF you only play to get from A to B through the story, that is.
There's 'win a level in the best time' (no thanks), 'win a level with least shifts' (no thanks) and 'win a level without dying once' (no thanks). I don't think the interface is up to it. To do those challenges, I'd rather the game be isometric and have an interface like a video editor where you could record and playback phrases of input.