This was actually pretty dang good for a first level. I do absolutely adore the good usage of default tilesets, and the custom music selection is top-notch.
A few comments I have about it, though:
1. I feel you could have put save points in more places? Specifically in parts where you're sent back more than two screens before you die.
2. This is more of a nitpick, but it bugs me that you have to enter the code in the castle twice so you can beat the level.
3. You could have made navigating the level easier with KS+'s map feature, but to be fair that would kind of get rid of the level's 'retroness' anyhow, so what do I know.
4. The bee wallswim thing that Sergio already mentioned. Kind of odd that that slipped past the QA testing. :P
All in all, a not-perfect yet still great level. I enjoyed playing through this one. Made me feel like it was 2010 again. ^u^