Not bad for your first!
It won't trouble the Daily Top Five as it is but it's a pretty good start! The basic platforming elements all work and the layout of the level wasn't bad!
Now you just need to get on with the fun part: presentation. Put a character in rather than a box that somehow jumps, add in some backgrounds and make the platforms something to look at. Unless you're going for a geometric feel, in which case take it and run with it! More edges, replaces the coins with squares etc. Take some inspiration from games like Geometry Wars which use the same idea!
Still, not a bad idea.