This is an excellent idea, you should definately work on this some more. It has a lot of appeal because it is social and creative too. It also brings back memories for me, I loved to play with level editors for games in my younger years.<p>I think though that you should allow people to play a level without signing in.<p>The gameplay does feel a little slow and generic though, you should work on making that more fun and a little more polished. For a well polished 2d game have a look at Cavy Story.
Not bad for your first web app.<p>I'd recommend that you work on making it easier for the user to play the game right away. Every click the user makes will result in a dropoff in conversion rate. Otherwise this is pretty interesting!<p>Keep at it!
The "(my first webapp)" in the title feels a lot like a link-bait.<p>Surely this isn't the first time you wrote HTML, CSS, and Javascript, right?<p>I mean this could very well be honest, but I really don't think it belongs there.<p>(I could be wrong.)<p><a href="http://ycombinator.com/newsguidelines.html" rel="nofollow">http://ycombinator.com/newsguidelines.html</a>
The logging in barrier is a deal breaker for me.<p>Not saying you shouldn't keep it, just letting you know that some people will not get past it because they don't want to.