Well, I have just completed the first quest, and whew! It's very good design. Secrets are just hard enough to find. Last Dungeon made my nose bleed, but it was a good challenge. Original ideas, like the Dark Maze.
Unless it has been said already, there's something I stumbled upon during testing, and it's still there. When you play the Flute near the top-left corner, the lake becomes walkable. If you go up, you get stuck. There should be something there to prevent the player from going up in the water.
Other than that, it's super fun. Some places with a bit of eye strain because of the mix of colors and textures, but nothing major. I'm going to try 2nd quest eventually, and report feedback. Good job on this hack, The3Dude!