Even if simple, the design here is good. It involves exploration mainly, with hidden bonus zones and shortcuts. Sometimes it can result a bit linear, but the author managed to keep the fun factory up by adding tricky obstacles. I disliked the fact that, in one of the castles, you had to grab an item while climbing. That's probably the only major design issue this hack has. The rest is okay, as said already.
The aesthetics are good as well. Mainly vanilla graphics, sometimes spicied up with minor exgfx like the cement blocks reskin and the SMB3 brick blocks. I loved some of the custom palettes, in particular the ones in the world 1's secret levels.
Not major issues here, although there's some rare sprite tile limits errors in the first castle.
Overall, 3/5. Not the best hack ever created, but it's sure worth a shot.