Not a bad concept. Reminds me a little of The Incredible Machine, just physics based, and I really liked that game as a kid. That said, I think this could use some more fleshing out; all the levels feel rather samey to me, and while it’s nice that it gets harder over time, the lack of new mechanics or new approaches to the setup got me bored after a few levels. There’s a bunch of potential ways you could fix this, but one idea that comes to mind is simply to give levels more complex layouts with static collision objects or something, rather than just different flag positions and number of flags.
I also found it rather annoying that the little balls you use to control the plank thing push each other around while you’re constructing the setup.