It's too easy, and the controls are weird.
When I say the controls are weird, what I mean by that is it's weird to switch from mouse to keybaord like that without there being any visual reason for it.
Also, far too easy. I had no problem solving every one of the levels. Here's what I would suggest, if you can do this:
your arrow keys control character A, Your mouse controls character B, which can fly and move the grey blocks around. The gray blocks can't go completely through other blocks, but they can be attached to any other block from any side. This means you can't just drag the blocks from anywhere, as there might be obstacles in the way. Perhaps some of the blocks cannot be lifted by B, but only pushed or pulled (because they are too heavy) out of the way so that B can get to the moveable blocks.
In order for character B to be convincing, I'd have the mouse cursor be a crosshair that B follows, at whatever speed B is capable of moving. If you click on a gray block, B then picks up the block, and continues to follow you around. Clicking again tells B where to put the block.
Anyway, I see promise in your idea, but what you've done here is very simple and rudimentary - as you say, it's a test - so I hope you don't mind my long-winded suggestion inspired by your little game.