Gameplay: (9.5/10)
Dang man, you've really mastered difficulty progression. Starts off nice and easy, almost relaxing even. Midway through, I'm needing to watch my jumps and be prepared to spin back to a safe spot. Near the end... well, let's just say I would've really loved a second checkpoint, lawl. In fact, that's pretty much my only complaint- I died. A lot. Most of the time, it was definitely my fault, but a few times there was a section that I just couldn't anticipate properly- the small hill on the second last pass of the final transition comes to mind (was not expecting the green platform after the rotating wooden platforms to pass through the hill and come out the other side. Even after knowing this, not being able to see it pass through meant my timing was off for several subsequent attempts). The bit with the "dangerous material" minecarts is another one that took a ridiculous number of tries to get right (would always hit the roof and fall short, I'm honestly not sure what stroke of luck let me pass through eventually), although, to be fair, you can try that one as many times as you want without needing to restart. I love your innovative challenges, and it was great fun, but failing repeatedly so close to the shine and then needing to backtrack from the checkpoint did get extremely frustrating (I can't even imagine what it would be like on a slower computer, with abort script notifications eating up even more time).
Graphics: (5/5)
Beautiful work here. I can't think of a single suggestion or critique, actually. I love how you blend different tilesets, and was particularly impressed by your use of wooden tiles... never would have thought it could look so great. Loving your use moving blocks as decoration and to cover gaps in the tilework, too.
Other: (3.5/5)
+0.5. Those dangerous minecarts are brilliant.
+0. Apparently, being a Music Duel, I'm obligated to at least mention the music bit. :p You certainly represented it literally, with rails (and minecart trains, of course) being an integral part of the level throughout, but it did feel a tad out of touch with the slower half of the level. More "just another background music" instead of a driving force in the level, you know? No points lost, however.
Overall: (18/20)
Amazing work. Love the attention to detail, and how you always seem to come up with some sort of new mechanic. My only advice would be to add another checkpoint nearer to the end.