I would resize the resolution to a smaller size, now I have to use the scrollbars to see everything, but I see you already know this.
For a first game this is not bad. This doesn't look like you just uploaded a tutorial project but really tried to make something yourself. Stuff you can add to make it better are of course music and sounds, animations etc. Putting some text in each level is really great I never done something like that because I have no writing skills but maybe you do and you can add some narrative this way.
Keep making games!