I found the puzzles to be on the simple side, once I figured out the doorway wasn't a waterfall when the door opened and I wasn't carrying a soul fire.
Spritework is solid, though for some reason your game is rendering a full spread of grayscale rather than 4 colors. I took a screenshot and it indexed to about 200 colors, and they smoothly went from dark to light gray. So, that seems to be a bug there. (EDIT: I re-checked the screenshot and all the colors are from antialiasing on the text, and a slightly darker dark gray around the key count. The rest seems to be working right.)
The lack of sound effects and music was a detriment, but you already knew that, given the statement of the game page.
Ended up playing until the room where the platform goes slowly around the room, and decided I was too impatient to wait it out.