Yes, as people have already said, it could have been a neat, simple game, but it's lagging too bad. I don't know why, though. Too many objects? The snow in the background? Time-consuming methods in Update?
When the lagging is gone, you could probably add some more variety to the levels (currently, the only obstacle are the walls, the only danger are the dark blocks). It's Unity, you could quite easily add e.g. a steep slope and a pitfall behind it, so it would require some manoeuvring ability to survive. And other things.
But the lags are a crucial flaw, so that should be your priority.