Just a note the color you used for those scores is bad and hard to see on a whit background.
Anyway, I played Koopa's Dugout and it was pretty well put together for the most part. You did a good job with enemy placement, and the difficulty is pretty fair. I did notice that you forgot to extend your walls and ceilings above the top of the level boundary so I was able to walk over parts of the level like right here:
I couldn't find anymore problems, so that's a plus. Also I think the Boo with a Koopa shell could have been used for way more than it was, it would have made a great gimmick but this level didn't really have any. Other than that though, the alternative paths are a nice touch, and helped the level a lot. One other thing I should say is that as soon as I was starting to think the level was beginning to be a bit too long is when I reached the exit, so that's a job well done right there. Nice work.